Mashup

Hey guys,
so im fairly new to mac (and new to the forums) and i have been playing around with garageband for a while and i realized that it doesnt have all the features that im looking for. I want to make a mashup of songs. (like Norweigan Recycling )In garageband you cannot match up the tempos of the different tracks so that they match. I want something that i can grow into and learn to use also, not just something that barely works. What software do you recommend?
Thanks
Adam

The best program for mashups is Ableton Live. it automatically adjusts the BPM of the accapella to match a separate beat or instrumental. It is soooooooo simple to do with Live.

Also, Logic 9 has a time stretching audio feature called flex time. I've had making mashups on logic since its release of Logic 9.