I have retired my AGP Q6600 HD3850 system. But good luck with your build! I can see you are having fun... I remember benchmarking and it was FASTER than an equivalent PCIe 3850 system. Early PCIe chipset days I guess.
I installed a gigabyte i-RAM with 4GB (4x 1GB) DDR. http://www.ebay.com/itm/GigaByte-iRa...#ht_873wt_1394
Even though (today) a software ramdisk is much faster than this SATA1 ramdrive, it is still an interesting option for an AGP build. Why? On an AGP system you are short of memory, with the 865PE(?) chipset limiting you to max 4GB DDR. And if you are running x86 then you are also constrained my Windows memory management, giving you just 2GB before /PAE etc.
So with a 4GB pagefile on the i-Ram drive, you get some pretty fast "paged" memory compared to HDD or even SSD. In fact, it worked so well, I had 2x of these devices in the system RAID 0'ed. I created 2x 4GB partitions. One exclusively for pagefile, and the other for temps, and manually pointed temp, web cache, winzip temps, etc. to it.
The system was pretty snappy.
If you are lucky, you sometimes see them going cheap on ebay... where a populated board essentially goes for the price of the DDR ram. If you have 4GB spare DDR knocking around, then it is worth $30-$50 just getting a board for the lolz.
WARNING - Those batteries on board tend to survive a power blip or reboot, but will not hold your data overnight if you power down the machine.
HERE IS A BENCHMARK of the i-RAM. Note that is it SATA1 constrained. So average read/write speeds max out pretty quick. However, random is fast compared to SSD. Note that these benchmarks are done on my new system not the AGP one. However, since the i-RAM is SATA1 constrained, the results will be pretty similar.