Extensis have a version of Suitcase for the Mac, so you shouldn't have any trouble in that respect. I've not met a font yet that hasn't worked for me.
I'll give EAC a try under VPC, but I doubt it'll work well. [edit] seems to be working fine
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afaik, the firefox extentions should be cross-compatible.
There aren't any iTunes plugins for FLAC yet, i've been looking. There are a couple of flac compressor/decompressor programs (I use MacFLAC) which will extract the WAV/AIFF so that you can recompress them using iTunes. ALC, Apple's Lossless Codec, is every bit as efficient as FLAC.