Been there done that with the 'OEM' retrofit - remember cruising the boards for TSX projectors.
If you think you'll have any inkling you'll want HIDs OEM, get it at the time of purchase. Unless you're really that crazy about 'em the time and money is much better spent on something like suspension or a supercharger.
Only issue with this is, its not even an option for a non-premium car. So it becomes a $4800 option instead of an $800 option if you really don't care for what the premium package includes.
I'll be doing a projector retrofit..hard to beat with parts down around $300 including bulbs, ballasts, projectors.