I was a PC user Sonar, moved to Pro Tools 7, then I went Mac. Started with Mac Mini i5.
Well if you buy a Mac.. I suggest a silver Mac Pro Tower 6 or 12 core. I have bought mine from http://stores.ebay.com/Charlie-Mac-PC
Running 12.5.2 and I added a USB 3 card to my tower as well.
The more cores the better from a plugin processing view point. I have a 6 core 3.33 that runs 50-70% usage
depending on Warren's track count and my additional tracks. Especially with Verbs. Abbey Road Plate
added 20%.
So I now have a 12 core 3.33 and it runs at 35% CPU usage.