raid is only if you use more than one hard drive and you want to set it up in raid. ide vs ahci. for ahci you will need to load drivers for sata during installation xp, if you hve vista then you don't need to worry about anyting as it's built in. ide is used if you don't have the sata drivers or you can't slipstream it into your xp. when i first used xp with my 500gb sata drive, it was in ide mode. recently i reinstalled vista with slipstreamed sata drivers.
honestly i don't know what the difference is suppoed to be in performance because as far as i know, it's the same. now i could be wrong and some benchmark can prove it. but i as yet have to notice some differences. in future if you add another drive it will also be in whatever mode you set it in.
AHCI stands for advanced host controller interface, this tech has it's speed increasing influence with raid and multiple drives.
Using only one drive, no need for it, use IDE.
One of the 32BM cache hard drives would be faster in all instances.