Looking for an inexpensive low power amp with exquisite sound

Buy a Prma Luna Prologue new for about a thousand.

I found an Audio Assembly SET 300B (by Sonic Frontiers) for $750, upgraded all caps and resistors (I also splurged on EML XLS 300B tubes that were well worth the price of admission), but this amp is amazing. The extra spent on the output tubes is not necessary, but very worthwhile.

Regards,
Dan 

The old Forte solid state amps sound great for the money. They usually sell for around $500 and were designed by Pass. If you don't want to deal with old equipment, Audio Advisor has a Nuforce STA200 amp they are selling for $500 that is getting some good press here. 
https://www.audioadvisor.com/prodinfo.asp?number=NUSTA200

Music Reference RM-10

I agree with tomcic601 the RM-10 is a great choice and works great with passive preamps. I run mine with W4S STP-SE into Reynaud speakers. Designed by Roger to drive his personal Vandersteen 2C speakers which it did with my 2CE Sigs with ease. The Nuprime badged Job amp is also a really good amp and a bargain. I could hear no difference between it and the Job 225 it was based on. There is one for sale for a good price on US Audiomart now.

https://www.usaudiomart.com/details/649450510-music-reference-rm10mkii/