BEST SPEAKERS AT A REASONABLE PRICE

There are many issues to consider.   

- What kind of music do you listen to?
- How loud do you want to listen?
- How big is your room?
- WAF

One of my all-time favorite systems belongs to a buddy who runs a pair of late 70's vintage KEF Calinda loudspeakers being driven by a Marantz 8B tube amp.  You can find Calindas for about $500/pair, but most are in Europe.  Hard to find in the USA.  I'd run a VTA ST70 to drive 'em and they can be had in kit form for about $800, and assembled for about $1000.

But you want to run your receiver and the Calinda is extremely revealing of what an amp sounds like.  I wouldn't want to run them on an Onkyo SS receiver.

What would be an *awesome* value would be to build the SEAS Thor kit, from Madisound, for a bit less than $2500.  A similar commercial loudspeaker from Joseph Audio sells for $12,000, so you get a good idea of the value proposition there.   If you're not up for doing the wood working, any kitchen cabinet maker could knock out the enclosures for you without much difficulty and depending on your budget, could offer any number of finishes.  One friend took his enclosures to an auto body paint shop and for $500, got something which looks very cool.

Paradigm speakers at any price level blow the doors off anything else in the same price range including their subs.

$2499 will buy you a pair of the already-mentioned Eminent Technology LFT-8b, and unlike the somewhat similar Magneplanar LRS, .7i, and 1.7i (all being magnetic-planars), which are a 4 ohm load and require a considerably stout power amp, the LFT-8b is an easy 8 ohm load (better for tubes) and requires less power. The Maggies are cheap, but their power amp requirements raises the cost of ownership.

There is a used pair of Focal Aria 936 speakers listed currently on Audiogon ( not by me) asking $2,100. I own both the Focal Electra 1028be and the Focal Chorus 836v in a second system. Very happy with both. Many rave about the Aria line and the 936 in particular. Pretty efficient/ easy to drive and very musical. 
I also agree with the recommendation to get a good integrated amp. Many can be had used on Audiogon that can meet your needs for under $1,000, including a Marantz PM-8006 for $899 that will easily drive the Focals, has a pre out for your sub (may not need with Focals for music) and has a built in phono stage if you want  to add vinyl. I have purchased over a dozen items used on Audiogon and have been pleased with every purchase experience.

the Marantz, the Focals and a Bluesound Node would be quite a nice system.   
Enjoy. 

—> Monitor Audio
—> PSB Imagine 
—> Golden Ear Triton

I strongly second the  Magnepan 1.7i.  If you have a lot of power and add a REL sub the sound will be hard to beat.

+ The Maggies are cheap, but their power amp requirements raises the cost of ownership.

Millercarbon is right in that if you really care about good sound that receiver is not going to cut it.  If you just watch video it will be fine with Best Buy speakers but you’ve come to the old guys here to learn about how to make your music sound great, right?  He’s also absolutely right about a center channel wrecking your sound:  2- channel is where it’s at for the best sounding music.

Wc1 is also right in that most of the recommendations for speakers you’re getting from here need much better and more expensive electronics to make them sound good.  
So here you are.  Getting mostly advice from old guys with their favorite traditional stereo stuff.  
You may be in the wrong place.  
Instead, have a look at this:

https://swanspeakers.com/product/m3a/

And go watch this:
https://youtu.be/YEx1_-wmgNI

of course I could be completely wrong and you really do want to join the ranks of us perpetually dissatisfied cranky old farts.... 

I like the idea of active speakers as they will sidestep the issue of amplifier adequacy. While I believe most actives are class D, my understanding is since they are voiced with the specific speaker in mind you get more positives out of that synergy than you give up in the arguably inherent weaknesses of class D. LS50s also come in active configuration with direct streaming and DAC built in. Not listened to them myself but heard good things.

I'm in about the same budget range as OP, although I've actually lowered my dollar amount seeing what's available out there! I started this hunt a couple of months ago looking at the Monitor Audio Silver 300, but in reality these are too large for my space - even though they're much smaller than the speakers I'm seeking to replace.

I like the KEF R100 for a warmer sound but they are clearing out the R500 floor standers for a good price. Heard good things about several of the ones mentioned. But you have to listen for yourself. There are so many good but different sounds to the same source. Also may want to consider Focal and Dali.

The R500's are 50% off right now, and it looks like that's my final choice. The size of the drives is right for the listening space. And $1400 (with lovely 10% CA sales tax) puts it in a nice spot. The R5's are only $2k, but the build quality isn't as high as the older ones. Heck, if the OP has the space, the R700's are $2k/pr. I've heard some people prefer the R500's because they blend more seamlessly with the UniQ. YMMV.

The Dali Oberon 5 look interesting but perhaps a bit small, the 7's on the other hand might be perfect for the OP. Cool design. Plus, they're not vinyl wrap like the Zendor.

I've always respected Focal speakers, and some fantastic prices have popped up briefly on the 948's. In fact, there's a pair at A4L right now in piano black for $2500. Probably because it's their last pair. NEW! That's a crazy great price.

Used KEF 104 @ about $500 pr.  

Reasonable price? Find yourself a vintage pair of DCM Time Frame speakers 500, 600 or 700, you'll be n pleased. Roughly $350-550 tops.

Open baffle speakers, like my recommendation (Emerald Physics KCIIs) don’t need no stinkin center channel

The upgraded KCIIs with carbon fiber drivers is available for $1999, delivered.

I agree with all who mentioned Vandersteen and Magnepan. I have MMGs in one system and 2CE Sig2s in another. Both are stellar at a lower price point. I would agree the Magnepans need quality power to sound thier best. I use a Parasound A21 amp.

I am also in search of a portable speaker for traveling what are some good options...