Check out LAMM, airtight and BAT, I know of more then a few folks who prefer Rowland amps using the single ended inputs which would leave BAT out of contention(on the VK-5 and VK-50 models only), however YMMV, what works for one persons system may not work for anothers. Seeing as your working with a good amp there shouldn't be much of a problem getting it to sound good, Cheers!
Tim
Tim