Power amp for Supratek Chardonnay preamp

I think the better question would be what power amp to mate with my speakers. The power amp to speaker interface is much, much more critical than the pre to power interface. Just about about any power amp on the market can be properly driven with the Supratek. The possibility of getting a power amp that won't mate well with your speakers is infinitely greater. I am not familiar with your speakers, but the fact that you are using a fairly high powered amp suggests that many lower powered amps are not suitable.

Ask Mick to make the gain adjustable (on the SupraTek), there is a knob he puts on the back of the chassis. This may be standard on the Syrah and Chardonnay but it isn't on the Cortese. Adjustable gain isn't an absolute requirement but it has its benefits when you are mating the preamp with a high-gain power amp.

I use the Sim Audio Moon W-5 with my Cortese. This power amp has excellent bass control with a little sweetness/delicacy on the top. It doesn't have the midrange palpability of a tube amp but SS amps never do and one of the reasons I got the Cortese was to compliment the Moon in this regard. I am please to report that the pair make beautiful music together.

I would hold off on making any decisions on a new power amp until you get the Chardonnay and get to hear how it makes music with the Plinius. By that time the Plinius should be broken in. If you decide to try different power amps I would consider Pass Labs X250, GamuT D200, Clayton, Blue Circle BC26, or Sim Audio W5.