Seeing as I assembled it last summer for around £300, I'd say its fairly average for a modern computer.
Now you mentionn stuttering, I get a bit when an AI car comes into view for the first time - presumably loading the model, but I don't get any high speed stuttering at all, not enough free ram to cache enough of the island perhaps causes it?
Btw, I run 1280x1024, high detail, no AA/AF, HDR off, and average 35-40fps. Upto 50fps when out in the sticks. Mild overclocking on the CPU & gfx card.



, then a Jagguar XJ220 also very fast, then a Caterham 260RS and a euhm euhm ohyeah a Noble M400 also top tuned very responsive good acceleration but my baby stays the Saleen S7, so ive ayone wanna compete against me on some highway or just mountain course add me on msn: 
(PC version of course)
, a Mercedes SLK55 AMG or smthn like that and lost, losts lots lots lots more...