If you go the PC route, you don't need anywhere near as much PC as most people think. For years I could edit hi-res video and mix 20-25 tracks of 24-bit audio with VST plugs with absolutely no problems on a 450MHz Pentium III with 384MB RAM - an outright Model T Ford by today's standards. The only thing I had some problems with were the performance of some convolution reverb plugs, and (in later days) running Reaper, both of which are major CPU hogs.
But other than those exceptions, the only reason people seem to think they need super PCs is because they have sloppy work habits and don't lock the tracks they are not currently editing. Because of this, they are askingt heir CPU to run a hundred different plug instances at the same time, which will bog any CPU down soon enough.
Stick with something like Adobe Audition, Cubase or Vegas Studio as your DAW software, and develop good work habits early and lock tracks that you are not currently working on, and you'd be surprised how little CPU you actually need to do professional work.
People look at me like I'm nuts, but it's the truth: ten years ago, we used to edit and produce broadcast digital (D1) video and multitrack audio productions on 90MHz Pentium I machines running WinNT4. These machines were used regularly by WGN-TV, The Muppets (Jim Henson Productions) and many Hollywood-based movie editors, just for some examples. So when I hear someone say they need a 3GHz, dual-core, blah blah blah nuclear-powered PC just to mix their garage band, I just gotta laugh and tell them not to be so goddamned wasteful with their CPU cycles.
G.