Author's Response:
I use Making Waves for the sequencing, and most of the effects etc. I use Adobe Audition 2.0 for enhancing MP3's, or just editing samples.
You can grab a demo of Making Waves at the official site (just do a google for Making Waves). It was made by a UK company, but it's not the most powerful of tools. I'm learning how to use Logic and Ableton Live at the moment. Thanks for the high rating, too!