Even with the 64 bit XP you are moving to a version that is rare to find all the drivers and help apps for. You know what you are doing and will accept that issue.
About better. I never found such a move to run better. Apps for the most part still are limited to 2GB RAM each just like before.
As to the SATA drivers, doesn't your BIOS do the old IDE emulation to avoid that? And such a driver would be from the machine's maker or the motherboard maker. It concerns me that you ask such because support is going to be non-existent. That is, you're going to get a little lonely.
So I got a fairly decent computer runnin XP since alotta apps I run are better compatible with XP, plus I like XP better than 7 anyways. (Though 7 isn't terrible, I won't even mention the other two...)
Anyways, I have 2 x 2GB ram in it and noticed i'm only using 3gb of it, so I was wondering if it would be worth it to upgrade to XP 64-bit. Once I thought about it, I realized that XP x64 is not all that common. From what I read, my 32-bit apps won't even benefit from 64-bit with added ram. Is this true? I also saw somewhere that XP only has SP2, What would this mean for me? One thing I absolutely need is SATA Drivers, though I don't think this would be affected by SP2?