130 sounds like a lot. but i mix memory modules all the time and have never had a problem. If you do anything that requires a lot of memory, it is better to go with the combined 768 instead of just the 512. You can never have to much memory, you'll need it eventually. If you buy your memory online, you might be able to get it cheaper. I suggest
www.newegg.com. They ship fast and are trustworthy.