Ah ayun, kasi I got this as a trade for some of my gear so not much choice. Vin's unit is a Kustombre and uses 6L6s, iirc. So dun pa lang talo na ako sa headroom and clean power. I think the Sunstream spits out about 15-18w.
ask mo si George if he can still do something about the headroom...baka babaan ung bias(?). di ko na alam pinagsasasabi ko hehe. it's been a while since I was so into oogling tube technology.
OR
if it has an effects loop. plug directly into the effects return. skipping the high-gainish preamp might give you more clean headroom by just using the power amp directly.
we did this in one of the siochi amp vid demos. it was in the carinosa demo ata...or the GT din.