$100K system build - % breakdown of spend

$50k to get the room 'right'.

$50k for the gear

I guess for a new house that works.
But a divorce can be costly, so sometimes the room just “has to do”.

Maybe that is why I like speakers with a narrower directivity?

How do you know if you spend that much money or buy anything different, it will sound better in your room? Your room isn’t ideal so I would caution any new purchases. You have to start with the room, a lousy room, you can’t expect much no matter what you spend 

I assume OP is using MSRP / new prices.  Which is fair.  But I would certainly consider used options for some of the gear.  In any event, I’ve been through a few system builds for two different rooms, and I have thoughts on his suggested speaker and analog ranges, as well as his expectations from ARC gear.  Feel free to PM me.  

I have never approached system building by budget allocation. I recommend instead that you get seat time in front of several different systems, of different types, to get a better sense of what kind of system (tube, stats, horns, big or low power, vinyl and all that comes with that if you want to go down the rabbit hole).

Although I hear differences in wire, I’d make that a less important factor for now. As others have said, you have to work with your room and maximize performance within it, given your objectives as well as the limitations of the room itself. Some people get way out ahead on room treatments- I use those too, but take a pretty minimalistic approach, using bass and corner traps, and rely on rugs and other things in the room and set up/placement to address acoustic issues to the extent I can.

Your sense of what sounds "right" will change with experience. Don’t limit yourself to demo discs of sonic spectaculars-- listen to "regular" source material.

My current system has been evolving since around 2006-7 starting with some good fundamentals that work well together (extremely sensitive speakers and SET power amps. This is all a matter of personal preference, and may not be the ideal for someone else’s ears).

But where an otherwise very good system was taken up a notch was simply a change in cartridge, a different power supply rectifier tube and other "small" differences that help "tune" the system to sound more lifelike to me in the overall combination of components in the room.

With so many variables, it is very hard to predict on paper how to "synergize" the combination of components, let alone allocate budget to each item of the combination as a theoretical way of predicting how it all comes together. That you must do by ear, and, if possible, with the help of a good dealer willing to visit your room and make some suggestions/help on placement, set up and dialing in.

This is not plug and play; it takes time for you to educate yourself about what’s out there and what combinations of equipment seem to make "magic" for you.

Treat it as a learning adventure. None of us is ever really "done" but much of the pleasure, to me, comes from learning and improving results over time.

@jrw1971 +1, particularly for amps, preamps & phonostages

@coys21 If I had that fun budget, would move some $ out of the the amp/preamp, keep the RELs for a while, and budget $20 for the tt + cartridge. At that level, may need a phono pre, but $5k w/b more than enough for that

I think one could hear the difference spending 2x on the analogue source without losing anything from the amp/preamp 

1) If were me, would start with the tt + cartridge

2) “One voice” on the electronics based just on my experience - amp/pre from same maker, ideally phono stage as well *IF* maker has a good phonostage. Just think this works better than mix & match

With one voice I can actually audition the electronics and know (roughly) what I am getting. The electronics were designed in relation to each other in the first instance.  Total guesswork / reliance on others if mix & match. (DAC can be its own thing - others will have better informed view of $5k dac vs. $10k dac, for example)

3) Amp vs Pre/Phono - to taste, but wouldn’t think twice if wound up at 50/50

A room that big opens up so many cool choices for speakers

Would be really interested in thoughts from others on the above - thank you

Tell us what you choose (and your process), and good luck!

Have a great day