Mac Pro the way to go
I was a die-hard PC only user until about 2 or 3 years ago when I purchased my first macbook of craigslist for $600. I bought the 13" unibody model with I think somewhere around 2.2 Ghz Dual core, 2gb of RAM. Slapped some more RAM in it (it honestly doesn't have to be Apple brand), sold it, bought a 15" macbook pro off ebay with a broken DVD drive. bought a DVD drive for it for 20 bucks, then resold it for 300 dollars more. Did the same thing one more time, ended up with enough money to buy a 2011 model (i7 2.2 w/ 16gb RAM) off ebay used in pretty much brand new condition. The great thing about Macs is that they maintain their resale value even years down the line. And as for music production, everything is streamlined soooo much better than on Windows; Example, the built in audio card supports multi-channel output and has almost zero latency when recording, and when using MIDI, all the instruments are found immediately without driver hassel, there are no 3rd party (asio) drivers needed at all, it supports almost all the VSTs I used in windows, and if I ever want to use windows I have it installed on a second partition (not only good for music, but games too

). I've gone through about 3 PC laptops over the course of a few years making producing on them a nightmare since I didn't know if my computer would die on me and I'd lose all my projects, but I can be as rough as I want to on this thing and it doesn't slow down at all.
Plus its just so damn sexy
tl;dr
traded on internet for years towards current-model macbook pro, got it, love it for music production. Never going back to PC.