Check out the Fulltone Full Drive II:
http://www.fulltone.com/FD2.asp
It has an overdrive, then a boost on top of that, as well as a straight signal boost (comp-cut) that boosts your current signal...in other words...if you like the tone of your amp, use the comp cut to crank it some more during solos.
www.Guitarvoice.com - Be Heard