You should check out the Full Drive II by Fulltone. Should run you about $150 bucks or less. I have a Tube Screamer (which I also love) but the Full Drive is where it's at.

It even has a bypass function to bypass the distortion and just boost your pure signal if you like the sound of your amp.

Check them out:

http://www.fulltone.com/stpframe.html

This guy has made these by hand since the 60's and still signs and numbers each pedal.