If you fancy attempting to wrap your noggin around synthesis then I suggest you stick with the software for percussion and spend a small bit of cash on something like an Evolver - http://www.davesmithinstruments.com

You can find one for probably around $350 USD used on lists such as Analogue Heaven or the Yahoo Evolver list. I bought mine from Novamusik brand new.

Check it out, its one of the best possible synths you can buy for the cash. Another option would be a Nord Micro Modular, which I'm sure will make it's way into my arsenal soon :)

-Chris