Quicktime + Persian will play all your typical files with no problem. For .ogm you'll need to use VLC. I don't really have any experience with MPlayer, so I can't say; I think I downloaded the wrong version of it.
And if you're that concerned, simply use Bootcamp. Your Macbook (because you're not spending money on an iMac, faggot) should have enough diskspace to be comfortable on both partitions.