Greetings,
I would say go with the Mac. iMovie and Garage Band are both great entry level software for video and music and if you don't need to do anything to fancy you may not even need Final Cut Pro. The Mac will give you an experience that is much more fun and Amiga like than you will have on the PC plus as you said you can run Windows on it when you have to since their are a lot more games for Windows.
If you have the cash it seems to fulfill all your needs the best. I never had a full flyer system however and have toy'd around with the idea of getting one just for nostalgia sake. Thing is anything I did on their that I wanted to share would have to be output to my Mac anyways to burn DVD's and make internet ready versions of.
Good luck with whatever path you choose.
