One great booster for the VOX type modules is the fireplace classic by covington effects.
http://www.covingtonguitareffects.net/Products.html
There are a number of boosters, some with knobs and stuff, some real basic. This will give you the Brian May/Queen treble-booster style tone that is really really awesome.
It isn't neutral, and will shape your tone, but in a great way. Use them on low/mid gain modules for a classic crunch. I'm really happy with mine!