Anyone have a suggestion for a active cooling unit for my MATX MB in a Q-pack 2?

You need to be much more specific. "Active cooling unit" could mean anything from a $2000+ phase change system, to a $5 heatsink with a crappy fan.

We need your budget, and the specific mobo your going to be using.

Something for over clocking , small enough to fit in my case most likely looking around 30 to 100 bucks. Something better than the very good Pentium D stock cooler.

With a little modding it should be possible to jam a Thermalright Ultra 120 eXtreme, the best air cooler on the market ATM, in your case.

If you don't want to start lobbing chunks of your case off then your choices become alot more limited. The Zalman 7700 is probably going to be your best bet.

if you're willing to raise your budget a little higher (10 bucks maybe), you can get a entry level water cooling kit. It's a lot better if you're thinking about OCing.