You're welcome! :)
I suspect Microsoft is going togo much more heavily to Vista x64 instead of XP x64. If you're buying a new OS anyway, you might as well go with Vista. The thing is though, I'd hold on to your current setup with XP x86 on it for at least another month. There are a few companies, like CMedia that should be releasing their x64 drivers sometime in April. I'd be very surprised if Creative Labs didn't have an update by that time.
You see, the issues with Vista aren't entirely the sound card manufacturers fault. From what I read, Microsoft eliminated DirectSound in Vista, and all there is is a semi-complete set of driver standards to follow. The only sound card manufacturers that weren't heavily affected were the ones that have essentially no features (no real EAX or DDL etc) available anyway. That's how a crappy chipset maker like REALTEK has a full lineup of drivers, while CMEDIA has virtually none, and Creative has crappy ones.
In short stick with XP 32 bit for at least 1 more month (probably 2) until you see some new drivers start rolling out. THEN GO VISTA x64!!! :)
Main/HTPC: Asrock 970M Pro3, 960T -> X6 3.4GHz, 4x4GB, GTX960, 250GB Samsung 840 EVO, Vizio 60" LED 1080p, Xonar DX, Win10x64 Pro
MediaServer: Asrock 970M Pro3, FX 8320E, 2x8GB, and a ton of RAID storage