Recommendations for modest budget

Amp power required depends upon Speaker characteristics, primarily impedence and sensitivity.  Keep in mind that that a low watt amp may sound fine most of the time but struggle with sudden increases in demand, either with music or with video.  Also keep in mind that power ratings for AVRs can be misleading, as manufacturers tend to sum what is delivered in each channel and report that number, so a 50 watt AVR may truly be 25 watts, for example, in 2 channel.  I once had a slimline Marantz AVR rated at 50 watts and it sounded awful and clipped easily.
 

I am in the same situation as the OP and a novice.  I found a great article that gave me a good starting point.  Using the other links provided above you can definitely get in under 2.5K for a 4K system. 

https://www.audioholics.com/recommended-systems/2500-5.1-channel-recommended-system

Question for the forum - as I evaluate some of the smaller receivers (50W per channel vs. 100W per channel) how can I evaluate if I will over power or under power a selected set of speakers?

Additionally, as I look at future expand-ability are there any concerns buying a 5.1 channel receiver and only hooking up 2.1 channels (or 7.2 and hooking a 2.1 or 5.1 speaker set-up)? 

My next biggest concern is dual voltage equipment as some of the places I live have primarily 220V...  Still researching that one. 

Sam

You can find a system within your budget. Just shop around and get your money’s worth.

There will be a member that says you need to spend $4000, and another member that will tell you a $4000 system is junk, you should spend at least $8000. And another that says... you get the picture. Bigger fish eat bigger fish, like everything, cars, houses, planes, islands, etc.

Just get a system you can afford and enjoy it, you’ll be fine. 

Best-

1)I don't mind used equipment at all.  

2)4k is important and I stream that content through an Xbox One X

Two questions for the OP:
1) Do you mind used equipment?
2) Do you need 4K Video?

AVRs become obsolete quickly and have very little resale value.  The market for non 4 K AVR is infinite and you can probably get a great piece for virtually nothing .If you insist on 4K you can supplement it with something like Apple TV as a source and as a music streamer to boot.  A decent BRP can be had for under $100.  That would leave the bulk of your budget for a Speaker/Sub combo, or again you might be able to score big in the used market here.  The upgrade as funds allow

Here's a great system almost identical to one I put together for my brother, and it sounds absolutely fantastic for movies and surprisingly good for music too.  Includes a sub that will get you down to an honest 20Hz so you'll really feel earth-shaking explosions, etc. in your room, and the critical center speaker really delivers the goods.  This system will make your soundbar sound like a bad joke by comparison.  All of it is new with warranty, and the total cost is within your budget at $1978.  All you need to add is cables/interconnects, and @grannyring here can build you some really good Dueland wires that'll work great and won't cost too much.  Hope this helps, and best of luck in your search. 

https://www.aperionaudio.com/collections/towers/products/intimus-5t-tower-speaker-stealth-black?vari...

https://www.aperionaudio.com/collections/open-box-closeout-speakers/products/open-box-intimus-5c-cen...

https://www.aperionaudio.com/collections/satellites-bookshelf-speakers/products/intimus-4b-satellite...

https://www.svsound.com/collections/subwoofers/products/pb-1000

https://www.accessories4less.com/make-a-store/item/yamrxa780bl/yamaha-rx-a780-7.2-ch-x-95-watts-a/v-...

For your budget, you should look for all used gears, used AV receiver & used speakers and used cablings, etc. Another advantage of buying used gears is most likely they are already fully broken in in the case of electronics & speakers, and fully burned in all the way in the case of cables. most likely if the seller had been using them for a while. 

Do you need an AV receiver that supports latest 4K HDR video pass through or not? I assumed you don't care about latest Dolby Atmos & DTS-X formats since you are only doing 5.1. Did you already have 4K/bluray player? Or is it just for cable TV DVR box/satellite TV, Apple TV & other streaming movie service providers? Most bluray and/or 4K UHD bluray players usually have built-in Netflix, Vudu, Hulu, etc. 

Are you going to be using your system for listening to music as well or strictly surround sound movies (HT)? 

I don't think that the OP is going to almost triple his budget and a decent sounding 5.1 system can be had for two thousand dollars, how do I know? Because I have one! Bought the speakers and sub used and grabbed a last year model of my receiver at a big discount because it was being replaced by a newer model.  Check craigslist for sub and there always seems to be a lot of home theater speakers on there as well.

Good Luck, TISH

Your $2K budget, is NOT adequate for a 5.1 system with receiver included. Simply being honest.

The tipping point is around 5K (not including cables or a basic power conditioner) for what you are considering. 10K ideally for a basic yet very good full 5.x.x system (which could also include a second sub and object channel speakers).

Aesthetics and setup of a 5.1 system are problematic AND you will encounter problems and costs you don't anticipate.

For your budget (negotiated price) consider this:

https://www.soundandvision.com/content/sennheiser-ambeo-soundbar-review

OR opt for a 2Ch system, for now, and build upon it when funds are available. This allows for very good speakers and receiver used (at $2K). Choose speakers that offer matching center and surround, etc. so you can add those at a later date.

At that budget, I’d check out accessories4less.com for a receiver. Personally I’d want something 4ohm stable and with pre-outs (so you have the flexibility for upgraded speakers and/or to add a separate amp later if you want to). The Marantz SR5013/SR6013 are $500/750, respectively, and they are solid, well-featured receivers. At this price range, Yamaha is another that is often recommended. 

For speakers, the same site usually has decent Kef & Focal speakers in your price range. You should also check out SVS, which has good value speakers and subwoofers. Should be able to find a good combo for your price range with either. Don’t skimp on the center channel (it should be the same brand and model range as the front R/L speakers), but it’s fine to save money on cheaper surrounds. If you have room for and choose large tower speakers for the fronted R/L, then you can probably wait on adding a subwoofer until later. If you go with bookshelf speakers, then the subwoofer is more critical.

A few ideas...
Option 1: ($50 over budget)
Marantz SR5013 — $500
https://www.accessories4less.com/make-a-store/item/marsr5013/marantz-sr5013-7.2-ch-x-100-watts-a/v-r...
SVS Tower System — $1550
https://www.svsound.com/collections/prime-packages/products/prime-tower-surround-system

Option 2: (over budget by the cost of the surrounds)
Marantz SR5013
Kef Q series front R/C/L 
—Q750 towers — $1000/pair
—Q650c center —$500 (currently out of stock but should come back)
Cheap surround speakers of your choosing.

Option 3: ($250 under budget)
Marantz SR6013 — $750 
SVS 5.1 satellite system $999 (or upgrade to one of their more powerful subs)

There are tons of other options that will blow away a soundbar for $2k, but hopefully this gives you some thoughts and ideas to consider. It’s also definitely a matter of personal taste, so it’s always best to try to hear speakers before you buy if possible or get them from companies with decent return policies.

Finally, and I probably should have said this first, it’s important to think about how you’ll actually use the system. Do you listen quietly or loudly? Do you love that feel-it-in-your-chest rumble of the low bass frequencies or get annoyed by them? Movies and TV only or do you also plan to use it to listen to music?..if so, how... streaming, vinyl, CDs, etc and do you already have these components?  Several components to connect or just the TV? For under $2k you could get a sonos 5.1 system that would be nice for TV and movies and add the ability to separate out the surrounds to use on the deck or in other rooms when you don’t need 5.1... that’s definitely added value and a great option for many people, but it has limited inputs and the benefits of these and other “wireless” systems means you need a power outlet near each speaker and it’s not the best bang-for-the-buck sound quality vs wired options, so there are always trade offs to consider. 

Best set of luck!

Good idea to upgrade from sound bar.

I really like Marantz receivers, and your best value is buying last year’s model at 60% of retail when the new model comes out. I got the SR5012 for $600 (down from $1k) when the 5013 was announced. You may be able to now get the 5013 for a similar amount since I believe the 5014 is announced. The nice thing about these receivers (not that others don’t as well) but they do great with latest HT stuff but also have nice music streamers for 2ch audio via Tidal/Spotify/Qobuzz etc.

For speakers, maybe aim to spend about $300-400 on a sub and $1k-1.1k on the remaining speakers (left, right, center, rear surrounds for a 5.1 system, couple pairs of rears if you want 7.1). Of these, the L, R, and center are the most important, and I’d devote at least $800-900 of the $1k to those three, with the remaining $100-200 spread across the 2 or 4 rear surround speakers.

Some brands to look at for the three front speakers in that price range: NHT, PSB, Elac, lower end Martin Logan, Klipsch.

Not sure if SVS makes a $300-400 sub but if they do look at that. Sunfire SDS10 would do a nice job as well.

Others will differ but I think at this budget don't worry about cables much - keep it very cheap.  AmazonBasics-level stuff is fine and stock power cords.

Good luck.