Guitar Compression

I am running my rig and am looking to tighten up my tone a little, and a friend recomended using a compressor. I know there are a lot of schools of thought on this and I am interested in any opinions yay or nay on the use of compression, I am also interested in any thoughts of where to use it in my signal path IE: before the preamp, in the effects loop. I am currently running a Mesa Boogie 3 CH Dual Rectifier, into 2 Marshall 1960A's. I use a Voodoo Lab GCX switcher and ground control to handle all of my amp channel switching as well as running my effects in my loop (midiverb 4 & Boss PS-5) it also runs a loop in front of the amp with my Cry Baby and an MXR Phase 90 in it. Thanks in advance for your help and input.
John