$1400 or so, and I did it in spring of this year. It's quite the beast and can run any current game at maxed settings, and I imagine it will be able to do this for a while (mostly due to its absurd amount of ram and beastly graphics card) though when I do hit a graphical wall I'll just put another of the same card in.
I actually built this system mostly for music production, which it also handles in it's sleep, but when it came to time pick out a graphics card I had to go big as I've never had a quality gaming PC and have always desired one. So far the PC world has blown my mind in how it's just better in every way.
Oh, you want to run old school games? Easy, and they can be run with a number of powerful filters that make them look brand new and even put PS1 games in HD (making them look really close to early PS2 games, although in this crazy strechless widescreen I still can't wrap my head around). OH, you want to do it with a DualShock3 using a bluetooth connection and rumble support? Done, easy.
Want epic titles you played on console? Done, cheaper (Sometimes absurdly cheap, all of the GTA games, including IV and the Episodes, for 12 bucks has been my favorite so far), better looking, and if it's a shooter with a way more intuitive interface. And of course some of the best old school role playing experiences can only be found on the PC (along with most of the good, non-japanese, RPGS), not to mention titles like STALKER.
What I think I'm ranting here is basically: PC gaming kicks ass, and if you invest in your rig it will make any current gen console look like a light-bright.
Edit: Oh, and that's 1400 for just the desktop and a good external sound card. I just hooked it into my TV and surround sound system. One thing though, you don't need to spend even close to that much to get a good PC capable of running most current titles, I was just building a hypothetical future PC. Seriously like expect to pay around 500 or less if you build it yourself. Oh, and I built mine myself as well, it's really not that hard although have a good friend who knows how to help you or you risk really fucking something up, and be ready to face error after error after error, but once all of that is out of the way it's the only way to fly.
The SSD and graphics cards where most of the cost I think. 
