During my search I found that a lot of the mastering software available will work on both platforms. My main method of searching is to go to Dogpile.com and search for music software or mastering software.

I also have found that most full recording programs consider themselves adequate for mastering purposes and I'm sure you can get a pretty good sonic product with any of them. I am not interested in spending thousands of dollars for a name.

I do believe that Mac supports Direct X or VST plug in products(I think), thus if your music software supports these you don't need to care if you have a Mac or PC.

Mostplug-inshave both Mac & PC versions. Waves is a prime example.

I've yet to find anything that will get a DirectX-anything to work on a Mac, but I haven't really looked for that too hard either.

BIAS Peak is my favourite two-track editor, hand-in-hand with the Waves Gold bundle. But I mostly use that for editing and clean up: any actual mastering I do is handled by T-RackS.

you can try our PSP VintageWarmer (Multi-Band limiter/compressor or even more).
Now it is also in MAS version so you can use it in DP.

Regards from Poland
Antoni Ozynski
http://www.PSPaudioware.com