[Naagzh]

Do you or your band/client have a PA system?

If so, you could send the already-recorded drums out of your Mbox and into the PA system and back into the room, where you'd place a pair of room mics (start about 4 feet high and move them around till they sound good) and record them. Then, after some EQ and compression, you can sneak these two tracks back in with the rest of the drum tracks for added ambience. Could sound much better than D-verb (although you should try that, too). Depends on the room quite a bit.