I tried all variations of treble/mid/bass combos. I even ran it with the mids dimed and the treble/bass off, which is really cool if you're into ZZTop type tones. The only way I could get the definition back was to drop bass, but then the tone sounded thin, particularily in relation to the clean channel. Adding the second cab helped a lot in that it filled out the bottom end more, so I could reduce the bass a bit more without it sounding thin... however at the end of the day I just didn't dig the C90 sound.
The Celestion Gold seems a pretty popular option, although I've never tried it myself. I figured it was more for people looking for the AC30 chime and I was more after the raunchy early Marshall vibe. I mention this because you may not be after the same sound I'm after, so take my opinion with a grain of salt.
On a side note, if you're one of those people who bought a Lone Star after seeing the Andy Timmons videos... Andy uses Vintage 30s.