Time for my $0.02. :)
Based on the information in this thread, I would also suggest keeping all of the RAM for speeding up the rendering but I would recommend getting it all from Mushkin using 12 GB total as you originally planned. The faster timings may help with the rendering speeds as well. The Corsair 850W PSU recommended is also a good choice. I have a lower wattage model from them that is going strong in a friend's PC nearly 2 years after building the PC. In that same PC is a Gigabyte mobo which has been rock solid. As such, I second (or is it thirds? fourths?) the Gigabyte mobo. For the same reason, I would recommend the SSD drive as a primary drive in the build along with a high powered GPU. The 5870 appears to be a good card although I have not had time to read reviews on it yet. For the processor, the 920 will still be a great improvement over a P4 in performance.
Regarding the Seagate drives, yes, they have had problems but so have WDs and so have other brands. I would not recommend avoiding them altogether. Instead read reviews and such to see if a particular model you may like is known for issues. I do that for any components I buy, not just hard drives. In the case of the Seagate problems, it was mainly a firmware issue which Seagate has since fixed.
One thing that I was looking at regarding your build is what will improve speeds. In this case, the Mushkin memory timings being faster mean faster response to memory requirements, the SSD provided faster read and write times, the video card should improves the results of the rendering and possibly improve the speed at which the rendering is done. (I'll admit I am not sure if the rendering is more CPU or GPU bound.)
carrizojim,
Regarding the set up not being optimized for rendering, the OP's primary complaint was the amount of time getting the rendering done so a build designed for fast performance should help.
Coolermaster HAF 932 Blue, C2Q Q9300 (Currently at stock speeds), Asus Maximus II Formula, OCZ Reaper HPC DDR2 1066 8GB 2x(2x2GB kit), BFG 9800GTX+, SupremeFX X-Fi, PC Power & Cooling S75QB 750W, 2x Seagate 750 GB SATA hard drive, Samsung SH-S203N SATA DVDRW, Lite-On LH-20A1L SATA DVDRW, XIGMATEK dark knight - s1283, Windows 7 Ultimate 64-bit