Jeemy's right - you could get some practice in using the Mackie and the Saffire, but don't expect it to sound better than your ITB mix. One of the major requirements for an external summing unit is large headroom (passive summers have infinite headroom), and the 802 VLZ3 does not quite get there. So, don't buy the Mackie if all you would want it for is analog summing.
ok. thanks again. i guess i'll just leave it at that.