Don't let anybody discourage you from recording real drums, These guy's round here are in love with those canned drums but me, if I can (sucker) talk a real drummer into playing on my songs I'll go for it.
It will always sound better,, ( then you go back and replace the drums with samples using audio snap ha ha)
It is a bit of a learning curve but if you bone up on a few good techniques it can be amazingly easy. Keep it simple,
I'd start with Kick, Snare and 2 matching overheads and see what happens.
Basicly if the drums sound good in the room, and you place those overheads correctly, all will be good. You really do need the Kick and Snare separate, next would be Hats.
Adding more mikes just adds more leakage and phase issues. Yes it is a good idea to have each drum separate, but you will need better equipment and take more time to get it right.
So you could get by with a 4 channel audio interface.
If you do want the big channel count then grab a Tascam us1800 for $300. They are perfect for recording drums. Nothing else is even close at that price once you get more than 4 channels.
You cannot use 2 interfaces at the same time with ASIO drivers.