Agree with BeefCake.. Sounds like you should focus on your videocard. Personally I have 512 mb RAM, it takes a while to load, but I run HL2, FEAR, CS:S, BF2 and so on on almost(!!) Highest quality... To be honest it sometimes take over 5min to load CS:S when the server changes map, without downloading a new one, and I have a 2000k/bit line... But I can live with it... So you should be fine with 1GB ram...
2 gigs will eliminate the large amount of stuttering in the beggining of playing a map(which annoyed the crap outta me, especially when i was in a plane or heli). it also helps alot with loading times.
well anyways, i don't have that much $ for at least the next 2 weeks to spend on computer parts, right now i have 150$, i'll get the ram and the real version of BF2, and special forces.