The answer to your question is somewhat dependent on the speakers you want to drive and at what listening levels. That said, there are lots of good suggestions above.
I own an SLI-80 with quite a few factory upgrades. Bought it used in the stock configuration and a couple of years ago had it upgraded. Really like the result. Use it to drive Merlin TSMs (8 Ohm, 87dB); not a hard load, but not an easy one.
Miniature tubes are all NOS. Have tried quite a few different power tubes (one of the virtues of the SLI-80 is the variety of power tubes it can accommodate). Generally rotated between Winged-C EL-34s (triode) and Gold Lion KT-88s (ultralinear) for a few years. Tried KT120s (ultraliner) on a lark and they turned out to be an extremely good match.The clean sound, improved extension top and bottom, and the effortlessness with which they handled the Merlins made them my standard.
Good luck in your search!
I own an SLI-80 with quite a few factory upgrades. Bought it used in the stock configuration and a couple of years ago had it upgraded. Really like the result. Use it to drive Merlin TSMs (8 Ohm, 87dB); not a hard load, but not an easy one.
Miniature tubes are all NOS. Have tried quite a few different power tubes (one of the virtues of the SLI-80 is the variety of power tubes it can accommodate). Generally rotated between Winged-C EL-34s (triode) and Gold Lion KT-88s (ultralinear) for a few years. Tried KT120s (ultraliner) on a lark and they turned out to be an extremely good match.The clean sound, improved extension top and bottom, and the effortlessness with which they handled the Merlins made them my standard.
Good luck in your search!