I'm not sure why you'd want to use a mic with this polar pattern in the middle of a crowd at a club/bar, but to each their own and all that. I'm assuming that these mics are not self powered, and therefore will drain the deck to a certain extent using phantom power. Yes, a pre-amp would be batter than using the internal pre on your deck, but all considered, it shouldn't be a significant difference. Unless you are running for a few hours without an opportunity to change batteries, there is no issue, just bring extra batteries and change them if you feel the need.