I agree totally with Gresh.
It's a good tube amp, don't mess things up by sticking something low end in front. IMHO the DS1 really sucks as a boost pedal. Vai's DS1 on the other hand is modded by Keeley, I'm sure there's some form of distinct difference. I've tried a stock DS1 as a boost and it sounds horrible.
A better choice would be a dedicated boost pedal in contrast of a distortion pedal per se.
Do check out the gear by Xotic Effects. RC and AC booster is the way to go.
Here's a video of Scott Henderson demo'ing the pedal, on clean and the dist channel of his Custom Electronics Amp.
http://www.prosoundcommunications.com/english/video/scott_henderson/index.html
The RC/AC is the next on my quest to become a full fledged pedal slut.
Chris.