:shock:If you have the cash to enable you to put 10,000-20,000 rounds of .45acp through a firearm in a short period of time, then I would imagine that you also have the money to be able to comfortably afford BOTH guns. So I say just buy both of them.
EDIT: The cheapest .45 ball ammo I've seen (other than reloads) is the Federal Champion line that can (sometimes) be found at Wal-Mart for around $16 for 50 rounds, and that is if you are lucky enough to find it. Let's assume that you can find it, and that you don't even have to worry about the 6-box per customer per day limit. That works out to $3200 for 10k rounds or $6400 for 20k.
I'm guessing the XD can be had for no more than $700. Let's do the math. Buy the Kimber, then just buy 2200 rounds less (using the above figures, this will save you $704) than what you had originally planned, and you have the money for both guns.
This is a no-brainer (for me, at least)