The PNY you linked to was 4GB and the Mushkin was 6GB, whats with that? Are you sure you require 8GB of RAM? 99% of people don't. If your not sure just get 4GB then upgrade if you need to.
I was planning on getting two packs of the 4GB PNY or that 6GB Mushkin on sale and then a separate 2GB Mushkin. I would expect that I'll require more than 4GB of RAM because I'll probably want to run Windows 7 with a Linux server in a VM. I imagine it's going to get tight with only 4 GB but let me know what you all think.
Thanks for all the great advice so far!