I am currently running Magnepan 1.7i in an 11' x 14' room with two REL subs.
Speakers need to be 4'-5' from the front wall.
I have used as little as 25 watts to 50 watts from a good tube amp. Only bass was improved with big SS power.
For $750 or less, you are looking at older amps. I had an ATI 1502 (225 watts @ 4 ohms) that did fine. Look for high-current more than just a watt rating.
Unfortunately, a lot of these older amps are due for service.