Lastly:
I thought that this inexpensive/well reviewed ($1500 300B based DH/SET) amplifier might be a fun option, but due to the size of your listening room I'm not certain if it would work.
I gathered that you would like to limit expenditures @ $3k or less.
In my opinion the difference between decent DH/SET and other designs (excluding a few OTL amps I've heard) is not subtle.
DeKay