I currently have 768MB of DDR400 OCZ Performance (has an OE heat spreeder) RAM. I can afford to buy a 512MB strip of the same but not a 1GB strip. However, I can afford a 1GB strip of some other brand's value RAM. Is this acceptable and what if any downside could I expect?

thanks, Craig

different vendors is trial and error..

the big thing to watch is that you are getting exactly what you want from your alternate vendor and the specs match.. as far as affordability.. i would check amazon.com
or pctoyland.com for pricing.. maybe you can afford your OE goodies..

Personally, I try to find others' reviews on memory. Let them waste their money before I do! ;) I've had situations where I've bought brand name memory, like Crucial and Kingston, yet still had memory compatibility issues.

Are you tuning this system for performance? If so, I'd try to stick with all the same brand and speed of memory, and even try to go for the same size DIMMS in all of the slots. If you're running a dual-channel board, that's the best way to get more performance out of your motherboard.