I have a friend with Kingmax PC3500, an X800 Pro softmodded to an XT, and an Athlon 64 3800+
his PC ownz, the RAM is very goog in his system, it is very good quality I must say
Kingston and Corsair are good brands too, they make good quality RAM, I find them too expensive though when I compare to Kingmax
Corsair and Kingston seem to be able to get away with selling higher price RAM because of their big names in the RAM industry