PC is the baseline for this machine. This is the configuration this machine has had for a few years.
PC+1 is after making a memory upgrade from 3gig to 4gig. Improvement isn't from the extra memory but that the motherboard accesses memory more efficiently when there are an even number of memory sticks installed.
PC+2 is after making a disk upgrade from a WD Cavier (1T) to a Seagate Barracuda (1T). Surprised there isn't any measured performance improvement here.
PC+3 is after making a memory upgrade from 4gig to 8gig. Since the memory is already in the optimal mode, adding more memory doesn't improve the score either.
PC+4 is after switching from an NVidia 7300GT video card to an NVidia EN8400 GS video card. Note the performance for Aero graphics actually goes down but the Gaming Graphics (DirectX) score improves a bit.
At this point, I got a measured improvement in the memory and graphics gaming scored. Not a big improvement but didn't involve a big expense either. Also, based on past experience, I think the hard drive performance will be improved even though the Windows Performance Index didn't measure one. I've found the Barracuda drives to perform very well in the past and especially as the disk gets more full with data.
PC+5 But, I was a little disappointed not to get that Gaming Graphics score up higher and to have made the compromise with a dip in the Aero graphics score. So, I made a different compromise. In the 7300GT card I had been using, I replaced the stock fan with an oversized Zalman fan to keep the cooling up but the noise down. The EN8400GS was even quieter as it is a fan-less card. So, I decided to try a 9xxx card even with a fan and see how that worked. The 9500GT card I installed has a fan but it is barely noticeable and since my "man-cave" is near the furnace it is hardly an optimum acoustic environment. But (as shown in specs "PC+5") this pushed the Gamin and Aero graphics performance up to the best scores yet.
PC+6 So, if one video card is good (and bearable with regard to noise) then two cards has to be better. Right? Well, my next upgrade was to go to SLI mode. "PC+6" has two Zotac GeForce 9500GT cards running in bridge-less (bridge connectors aren't on these cards) SLI mode. Improved the desktop (Aero) and gaming graphics scores. Not too much noise and better performance. Nice. At this point, the CPU is the constraining factor and that was sort of my design target for this series of upgrades.
This looks like the configuration I will stick with until a build my Sandy Bridge system.