Some thoughts on two I've personally owned.
Rogue Cronus Magnum II (not the most current III). My experience, others may have had very different experiences.
Pros: Located in America, nice people, you can call them on the phone. Very heavy and powerful amp, reasonable price, good sound.
Cons:
Attention to detail is poor. Mine came with the center screw, that secures the top cover, cross-threaded (I had to shear it to get it off). On the CM this is a big deal because to change from 8 ohm to 4 ohm speaker taps you need to remove the top cover. My unit came brand new and drop shipped directly from the factory, no one else had touched it.
Quality. Generally a noisier amp over all. Doesn't present a silent, black background. The input selector switch failed while the amp was sitting unused and must now be replaced by the factory. It may or may not be related to that specific switch but when it was working there was bleed-over from a not selected input to the selected input. I also noticed crackling sounds when moving the volume knob. Very faint but noticeable. Can't speak to the III, but on the II, the headphone amp is quite poor.
Other. The amp is very large (big footprint), heavy and runs quite hot so you need a large flat open surface to sit it on.
PrimaLuna DiaLogue Premium Preamp and DiaLogue Premium HP amp.
Pros: Excellent sound quality. Wonderful mid range. Dead silent, deep black background. Controls work perfectly and are a pleasure to use. Built like a tank, excellent attention to detail and build quality. Much more attention paid to the aesthetics, overall quality, fit and finish. Still quite heavy but not as large a footprint as the Rogue.
Cons: Above your stated cost target. Not the be all, end all for detail and speed. Beautiful for the human voice, acoustic instruments, music recorded in a real space (nuances, openness, etc.) Really large scale music starts to push against its limitations. Runs hot (all tubes do). My room is about the same as yours and it can get uncomfortable in the summer time with extended listening. Cost, even at used prices you might find it hard to get the separates for $3k (combined they were about $7k new).
Final thought. I strongly suggest the PrimaLuna. Very high quality. Very nice sound. Perfect amp for someone new to tubes. It works perfectly, you can roll in any (appropriate) tubes you like. I have had two tubes go out on me. Both were easy to diagnose, order replacements, plug in and keep going like nothing even happened. I suggest you watch the used market. You can stretch your budget a bit and go with separates or choose an integrated and stay within your budget.
Hope my experience is useful info for you.
