Jeff,
I am very experienced in both Mac and PC. I use Mac at work and PC at home. I purchased a Dell Precision 690 for my home unit because at the time I purchased it Adobe had not yet announced it was going to make the Adobe Video production Bundle for Mac. I am a firm believer in the Adobe video production bundle. I like FCP however, the full integration of all the softwares in the adobe bundle make the work flow seamless and I do my own motion graphics and audio editng. I realize their is the FCP bundle but After effects is an essential and motion can’t compete with it. I would prefer to have a Mac now that they are coming out with the adobe bundle for both and some day will go to Mac.
I would get the new Mac Pro specs would be as listed below
proccessor
2 2.66 GHZ Dual intel
Memory
4GB
Internal Hard drive
I always default to 500 gigs even if I have plenty of external drive space.
Graphics Card
4 x NVIDIA GeForce 7300 GT 256MB
I hope this was helpfull Jeff.