I just built a new system and stuck an mSATA SSD onto the motherboard as a 20GB cache drive. Makes a big difference to the system and is essentially transparent to the system so it's almost like having a really big SSD drive. Managed to scrounge some parts as otherwise this would usually be totally extravagant.
It's pretty uncommon to have any real issues with an x64 system these days unless you're relying on old hardware/software. Unless you need >4GB RAM then there's not really much benefit to x64 anyway in most cases, to get around Microsofts arbitrary RAM limitation.