Tone King Falcon Grande: Anyone played with different tubes?

[BobL]

I've been playing a Tone King Galaxy for several years now, and it's a totally killer amp, but... big. In an effort to simplify for a new project, I was looking at smaller amps and simplifying my rig into something that would be easier to cart around (my goal was to carry my entire rig to a 3rd floor practice space in one trip), and decided to give the Falcon Grande a go.

I've been pretty impressed with it overall - the three voicings are nice, the size is just about perfect, and w/ the built in Ironman, the tone never suffers based on volume.

The amp gets along incredibly well with my tele, but my results with humbuckers (namely Lollar Regals in my BiLT) have been more hit and miss - cleans are good, but the tweed/lead settings seem to get too fuzzy too quickly, even on the low input.

Curious if anyone has one of these and has played around with different types of preamp tubes and found anything magical...