Need advice on next step

I recommended the Sonic Frontiers SFL-1 to a friend with a similar amp, i think this one is a perfect match for it. You should give a try.

I also like SFL-1 but also would add a good quality SS preamps such as Classe 60.

Any CJ preamp would be the natural match. You just missed 3 reasonably priced CJ preamps here on Audiogon. A Sonographe SC-1 for $260. This is probably the preamp sold with your amp. A PV-6 for $300 and a PV-11 for $750. By sticking with the same brands you are more likely to get good sound. Mixing brands is always risky. Keep watching more will show up.

head over to deja vu audio in mclean va. nice people and no pressure and lots of interesting stuff at all price levels.