Forgot to mention 1 GB RAM would be good. Also hyperthreading or dual core can provide a performance boost.
I don't care about SP since devs started to screw up the movement for some reason. I already hated that in JO and JA. I prefer the MP movement in SP just like in q, q2, jk for instace. I dunno about AvP and Unreal, but indeed D3/Q4 SP is boring as hell, not only because of the lame movement. The story is q2like the gameplay a pain in the ass.
Q4 multiplayer mode is ok now. Fortunately the movement is Q3like and also features sliding and ramp jumping. With the 1.3 id/raven managed it to improved multiplayer alot. Also they added a load of maps and one new weapon.
Some peeps whine it's too much Q3, others say that it's not enough Q3.
Maybe most are just pissed off cause the game requires more hwpower than they can affort.