I seem to be stuck in the 'V' shape on the GEQ. I use that shape for IIC+ and it sounds great. I'm sure there are other shapes that sound great, but I never venture outside of the 'V. I'm interested in how everyone else uses the GEQ to achieve the tones they are after. I am sure the V limits the tones that can be coaxed out of this amp. I'm sure I just need to experiment, but thought I'd get some insight from the board until I have a chance to play again...
Getting a good tone can be tricky for many reasons. One, the Fletcher/Munson curve makes tone appear to sound different at different volume levels. A tone you create at bedroom volume may not sound good at gig volume. Two, Anything you hear long enough sounds "right" once you get used to it. I, myself, have been guilty of playing a bad tone for so long that good tone sounded "wrong" by comparison. Three, it ultimately has to fit the context of the band. For example, my tone that worked with one band just sounded muddy with another band. It's because the bass players in the different bands had different sounds and I had to sculpt different tones to work with the different bassists.
From my experience, I think the best way to find the right voice is to record the whole band playing and evaluate the playback a few days after your ears had a chance to recuperate. One of those little pocket-sized digital recorders is perfect. Then figure out if your sound really worked and, if not, how to fix it.
If the recording is muddy/boomy, you probably have to many lows boosts. Take them out. That's what the bassist is for. If you find you have to play at crazy high volume to cut through, you probably need more mids. If it sounds messy, you may have too much gain.