Good Question
I too have been hoping there is a way to play Counter-Strike on the Mac. However, I thought that using Virtual PC might be a better route. After sampling the current iteration of VPC, however, I've come to the conclusion that Windows XP on VPC will yield a framerate of less than 1 frame per second. However, Windows 2000 might be a better bet.
I think using KDE and WINE would be far more taxing, chiefly because you are using multiple emulators; further, I'm not sure whether WINE was designed for the PowerPC architecture.
I'm also a CS addict; I'm more a 1.5 man myself, but I've been playing 1.6 lately. I am very unhappy with the lack of updates in CZ, and as such, I refuse to play it. However, to satiate my need for CS, I think I'm going to get a ThinkPad. If I were you, I'd check out eBay for some laptop deals. You can probably get a used notebook that is more than sufficient to play CS for less than you'd pay for VPC and the Windows OS.
If you do figure out a way to play CS on the Mac, be sure to post it ASAP.
Mike LaRiviere