I currently have a Boss DS-2 and a GE-7. When I run the DS-2 on my dirty it sounds bad. The boost of GE-7 is not really that noticeable on the dirty channel of my Studio Pro 112. I was wondering that by getting the MXR distortion III would it eliminate the need for my 2 current pedals.

Not really, its nice, but if your looking for a lot of distortion then its not going to. Its got some classic crunch for maybe hendrix or ACDC, but at max it can only pull off so much. No metal.
"Guitarmen, wake up and pluck wire for sound, let 'em hear you play"
-Charlie Christian
"You have to give people something to dream on"
-Jimi Hendrix
"I try to make any guitar do what I want it to do"
I dont play much metal.
I usually just play Rush, GnR, Aerosmith, Van Halen type of stuff.
I'd go look for a ProCo rat, probably way more flexible than the MXR.
Peavey 5150
Mesa Mark IV
Mesa Single Rectifier (Series 1)
Fender Custom Shop Tonemaster
Roland Microcube

-Whitebox OS 1x12
-Port City OS 1x12

Digidesign Eleven RackAxe Fx Ultra