If you plan to order on line, be sure to contact your credit card company and let them know you will be placing the order and give them the amount. Some credit card companies may not allow the transaction to go through until they contact you to confirm it, especially if it is in the $600-$800 range.
That's precisely what happened to me when I ordered my 32GB/3G iPad 2. I have an excellent credit rating, but the company (BOA) would not approve the transaction because they thought it was fraudulent. Maybe the fact I got up at 4 a.m. launch day to place the order had something to do with it, but I was furious they didn't contact me because by the time I discovered it, the delivery time had changed from two weeks to four weeks.
I switched to a different card and fortunately Apple was quite terrific and kept my order in the original delivery queue.
Your other option, which will appear on the online order site, is to split the purchase amount between two credit cards.