http://en.wikipedia.org/wiki/Boot_Camp_%28software%29
Mac engines?
Shredder for Mac is pretty decent positionally from my understanding of things. Stockfish is a good option for pure strength with the added bonus of being free.
There's a free trial of Shredder Classic, I'd recommend having a look at that. Failing that, VM Ware or Parallels allow you to run Windows while you're using OSX and give you access to all Windows offers chesswise.

The best choices I've found for OSX are (in no particular order)
Deep Shredder
Deep Hiarcs
Stockfish
But to echo xstagex and nesf I recommend you use VMWare. That way you can run any engine you can think of, multi-core ones as well; and you can use chessbase. vmware in full-screen mode is indistinguishable from a PC, but you can switch back and forth between mac and pc without needing to reboot, you can even keep the pc stuff running in a window on the mac desktop.
I gave up waiting for chessbase to port their stuff to osx years ago...
Regarding you finding Hiarcs not good enough at positional evaluations, which engine to you reckon is the best for that?

From what I've seen Rybka and Stockfish seem to do better with positional moves than others. But to be clear, Hiarcs kicks my butt all over the place. But it sometimes chooses moves that don't appear natural to me. Whereas some of the other engines, which still beat me to a pulp in easy mode, are making moves that look like moves I'd choose. My desire is to use an engine that I can understand what it's "planning."
(Yes, I recognize that engines don't plan the way people do. However, the tactical and positional evaluations are functionally similar to a plan if one looks at them that way.)

Look around for MAC versions of Stockfish, Firebird, Houdini (all free); Shredder, Fritz and Rybka (all not free, but you can probably find older versions dirt cheap at amazon or eBay - IF available in MAC that is).
I wouldn't feel guilty about getting a pirated version of Rybka, but not from anywhere online (only from someone else you know).
BTW what exacty (or even inexactly) is wrong with Hiarcs positional evaluations? I know from personal experience Fritz 12 tends to evaluate = positions as = in my turn-based games (once they're over of course) and then ignores several moves and then finally points out I'm busted (which I already knew). The easiest solution is to just set it on infinite analysis of each move in the critical sequence where I went from = or =+ to busted since Fritz doesn't seem to be able to do so on its own.
Note there is an XBoard install available from WinBoard forum that was specially prepared for Mac. ( http://www.open-aurec.com/wbforum/viewtopic.php?f=19&t=50428 ) It includes Fruit and Fairy-Max, (I think), but it can be used with every UCI or WinBoard engine.
Any good Mac engines out there these days? Or are we macites still stuck with Hirarchs as the best we can do? Which is considerably better than myself, but I'd like to find an engine that is better at positional evaluations.