To begin with, here's the performance of the existing hard disks in my system (all of which are 7,200 RPM models). On the graphs that follow, the blue line is sequential read performance while the yellow dots give random access time. The first two drives are 500GB Seagate Barracuda 7200.10's (model ST3500630AS), which were reasonable drives when bought for the initial build of Khaos back in 2007:
These results are broadly in line with the specification, which is not bad for 6-year-old drives. The first drive is probably slower due to being the boot drive, while the second one gets very little use.
Next is a much older 160GB Seagate Barracuda 7200.7:
The sharp drop in performance at around 45% was due to my music player changing track. See, I said these were very rough-and-ready benchmarks! Again, the results are broadly in line with the rated performance, though significantly slower than the earlier two. Using this drive for the pagefile in retrospect might not have been the best decision (it was chosen as it wasn't the boot drive, and the other 500GB drive is normally spun down).
And finally, this is what a shiny new fresh-out-of-the-box 256GB Plextor M5S SSD looks like:
Note that this is merely very fast - for crazy fast, I'd actually need a newer motherboard or a SATA controller card as my motherboard only has SATA-II support. Crazy fast is, according to the specs (and they are accurate), 520MB/s read and 390MB/s write.
Medium-term the intention is to use it as the boot drive for Windows 7, but there's some preparation to do before the upgrade. In the meantime I think I'll just format it and dump the Windows XP pagefile there (which being a single large file won't cause issues with the lack of TRIM support in XP).