Simple answer. Are you a gamer? If you answer yes, then you can forget about a Mac.
Wait about a month, if you can. Ivy Bridge will be released. Otherwise, get yourself a decent build with an Intel i5 2500k CPU. You can get a new PC with that processor for about $700 or more. But if you can wait, do it. You'll also be able to have a motherboard that supports PCI-e 3.0. Those are actually currently out, if you want a six-core Sandy Bridge processor. I don't know if it's worth the extra price, though.
In 2007, I had my PC built by CyberPowerPC. I will say, there are some negative reviews about that site, most of which come from "Enthusiasts". I never had a problem with my PC at all. In fact, it still works. My only complaint, is that it's too loud and I didn't have it built well for overclocking/cooling. I've upgraded the GPU, hard drive and RAM because I needed more power, not because of a malfunction. Those parts worked fine til the day I upgraded, but I'll be honest, I wouldn't bother selling them, they're useless now.
If you're going to get a new PC off of a website like CyberPowerPC, or iBuyPower or some other site, I would suggest for now getting one without the OS installed. You can download Windows 8 Customer Preview for free, and it's good until 2013. Then, just buy Windows 8 OEM and do a clean install. Keep in mind, OEMs are tied to the motherboard, and there isn't much support for it. So, you have to know what you're doing when you install it, not that it's all that difficult, anyway.
I'm about getting ready for a new upgrade, myself.
Again, to me, MACs are useless. Then again, I prefer Microsoft products (MS Office) and I'm also a gamer. Generally, developers will make games for the PC, since Windows is used more in the home PC over Mac OS.