I wouldn't mix and match RAM. I know it has worked and should work but still a tricky proposition with one of the two most important and troublesome parts of your computer.
I personally use 3 128Mb KingMax PC150 sticks in my system and can only say good things. Although keep your eye out! There are two different versions of the PC150 128Mb DIMM. There are Version 1.2 sticks and 1.0 sticks. I've read around that the version 1.2 are much better. Fortunately I ordered a stick about 6 months ago and got the v1.2. Then, about two months after that, I ordered some more RAM from the same vendor assuming I'd get the v.1.2 again and I got two sticks of 1.0. I was pissed and they woren't very helpfull. I did however just pop them in and actually I can't complain, everthing is good. So who knows.
Jon