I was under the assumption that RAM and maybe hard drive upgrades were the only BTO options performed at local Apple stores. If I remember correctly even Apple states on their on-line store that selecting the X1900XT may result in a delay in shipment.
Thanks everyone. I guess I'll just keep waiting as I've been doing since November. First I was waiting on a Mac Pro refresh, it came and went and was nothing exciting. Now I'm waiting on the announcement of Tiger so I don't have to buy the upgrade a month or two after getting my Mac Pro.
So much for waiting until Leopard comes out, now we're looking at October for that. Seems silly to wait until then. I'd rather have the mac pro now before I need the money for something else...