Would you consider a passive preamp?
If you bought Marbles' Bent passive, I am sure it would sound very, very good with a few different amps:
CI Audio D-200's
Odyssey Mono Extremes
Butler amps
Belles Reference 350A
Dodd 120's
I have heard the D-200's, Butler amps, and Dodd 120's with the HT3's and all are very enjoyable and could be a cornerstone of a great system.
George