my friend has the almost exact same system and thats where he tops out if he wants absolute smoothness all the time (not just when there up to 5 models on screen). jedi knight 2 is a freakin' awesome game. do NOT play multiplayer before you have played at least most of the way through the game. for 2 reasons at least:
1) you will suck, all the other will have more (and better) practise and will always be better then those who play multi only-no matter how long. single player allows easier adjustment into the game...
2) single player actually has a very good story too it, and there are some classic stand-offs that'll leave you smiling and say "damn i love this game". playing multi will ruin the experience of gaining the lightsaber and the force powers. you'll already know what to expect and one of the drives of the game is the lust (lust? does that lead to the dark side?) for more item/force powers/the all power lightsaber which you dont have in the begining.
i made the mistake of playing multi first, dont do the same!!
the multiplayer is awesome and intense, as well as the single player is. The game does have some great graphics, very smooth animation and great looking models. ai seems to alternate between being very slow dumb to very fast and intelligent. a bit of advice, unless you have a radeon 8500/g3,4 class video card, dont turn on the volumetric shadowing it will look like crap and will slow the game down a great bit.
oh yes, also, get the collectors tin- it comes with a pimpin' key chain!