Trying to find out a good offer for a used gaming laptop.

I am looking at buying a used gaming PC from a work friend. He was kind enough to provide me with the details. He asked me to make him an offer and I don't want to low ball the guy. Heck, I don't even know where to begin! I want to give him the price for the machine with the parts it comes with. He will not be including the HDD or RAM, but that is OK. I can get a deal through my work, so I am not worried about those bits and pieces.

Here is the information he provided:

Pro-Star (Clevo) P151EMx
Intel Core i7 3610QM (Ivy Bridge) @ 2.30GHz (8 CPUs)
NVIDIA GeForce GTX 670M 1.5 GB VRAM
Intel HD Graphics 4000
15.6" Matte Display 1920x1080 (32 bit) (59Hz)
Windows 7 Professional 64-bit

I have personally seen the computer. It is in great shape for being about 2 years old now. There are only minor wear marks on/near the touch pad. Keyboard functioning fine. He said he had some warranty work done and the screen replaced about a year ago but it was replaced with the exact model as the original. Otherwise, it is flawless.

Like I said, I am not trying to low ball this guy. I can also find out more information if given a little direction. He is a coworker and generally a nice person. Any help would be greatly appreciated in coming up with an offer. Thanks in advance!