As the owner of an early-2009 octo-mac-pro, I am very interested in learning about how to max that system out to the gills.
For instance, I am under the impression that it is now possible to boot from a pci based SSD card on that system.
Further, I believe it is possible to add a card that gives me USB3/SATA3 (although if I am booting from PCI, I don't really care if my slow mass storage internal four drives are SATA2).
Finally, I think there is some apple-blessed video card that is quite a bit stronger than the original GT120 cards I have in my system.
I've seen bits and pieces here and there about maxing out a mac pro and bringing it very close to "modern" but it would be nice if it was all in one place somewhere...
FWIW, other than maxing out the ram, I really have no problem with the existing RAM options and the dual-cpus that I already have (which bring me to octo-core). Even 8 years later, the machine is not slowing me down at all in the cpu/ram department (and I only have 6 GB).