Several others touched on this but I'll reiterate... I think EQ pedals
are particularly powerful for use as a solo boost/cut through. I usually play live through my first gen 5150 rig, and because I like a really thick, heavy, chunky rhythm sound I have the native EQ set up to deliver that. Tht also makes my cleans nice and warm which I like (5150 uses 1 EQ shared by both channels). However, when it comes to soloing, such an EQ means your solos are totally lost in the mix. I use an EQ to really boost the mids and add just a few extra dB for solos and it makes a huge difference.
EDIT: I realized I forgot to specify what EQ I'm using. I use a Boss Gt10 through the FX loop. I only use it for FX loop stuff - reverb, chorus, delay and EQ. I have a "solo boost" EQ I've programmed and just toggle it on and off.