Judging from other specs and performance it should be okay. One thing to note is that I think the seller should know what that stuff is worth and might not shift on the price.
This. $600 is a good price for that system, assuming it comes with a legit version of Windows. Even if it doesn't, the price is still a pretty good one. Claiming you could build it yourself for $600 is likely to get you laughed at though, for two reasons: 1) I figure the parts are probably 700ish. 2) If you could build one yourself, you probably wouldn't be buying a used one.
If you wanna nickel and dime him down, you can give it a shot, but I would strongly advise against "I could build it myself for X" as a bargaining point, unless you know you can.
$600 is a good price for the system though, especially since the guy seems to be throwing in a monitor. If I were to buy that system, I would be willing to pay $600 for it.
EDIT: I'm going to assume that Windows -may- be pirated, or he used the same install disks on his new computer he replaced this with. You can ask if the W7 disk is included, and he might say yes, but I get the feeling that he'll probably say no, or at best offer to burn a copy of it for you.
Also, ask if the Windows install on there is a fresh install or whether it's being sold as-is, and if so, ask if he has taken all of his data off of it (unless you want his data? I dunno, could be some quality **** and free games in there; could also be viruses and keyloggers). Edited, Jul 25th 2010 9:12am by Mikhalia