Nobody flame me but, do you have the approximate min requirements yet. (note the word approximate). If you do please dont say you dont know yet, instead post them because we could all benefit from them!!!
No, CounterStrike and Half Life are not Quake 3. They are both using modified Quake 2 engine. CS is actually even more heavily modified obviously. I recommend you get the Quake 3 demo from somewhere and run it with everything turned on and a nice huge resolution. If it's nice and smooth you'll have no worries.