First of all, for every microphone, you'll need a channel of preamp and a channel of A/D conversion on your breakout box (not sure, does your Delta have 4 channels?).
Also, I would strongly caution you not to try a gazillion mics (7 or 8 is very tricky). It's a lot easier to use 3 or 4 . There are fewer problems troubleshooting. Do a search on "recorderman" and "drums" and you'll find a really cool way to record great sounding drums with 3 mics.
BTW, it also helps to have nice microphones, nice preamps and mostly importantly, a good drummer playing nice drums, tuned nicely and played in a nice sounding space.