MacDaddy

Mids are key!  Sometimes I find a scooped tone that sounds great in headphones gets lost in a live mix.

There are various reasons why it might not sound as expected. Earphones will have a very different frequency response to that of the speakers / system you are plugging in to - even if the brand say thay are flat response, most are definitely not. Then you have the acoustic effect that the room space has on the sound versus the enclosed sound of headphones. (If you've had a chance to play with ARC or Sound ID or REWS, they can help us understand exactly how much the room space plays in our bass sound (and why IEM mixed can sound wildly different too). Oh and finally, those pesky Fletcher and Munson types with the loudness curves and how we perceive frequencies at volume (versus next to our ears inside headphones). Take those in to consideration and it will get a lot easier, but nothing beats getting in the space with the gear you're going to use and craft the patches on those. I suspect you know this anyway and, having a rough patch to bring to rehearsal and then tweak at the time isnt a bad thing at all! Good luck!

And the result from last night's rehearsal - inconclusive.

I went through an old Ashdown head through an old Ashdown cab. The synthy patches needed more fuzz, nothing cut through quite right, and levels were not consistent between patches. All issues I did not have with headphones (a cheap Behringer pair). Should have taken my own gear. Next time I'll at least take one of my own amps.