For your condenser, you will probably need phantom power in most cases unless you have one that uses a battery. Your best bet would be to get a preamp with phantom powere because the 840 preamps aren't very good. Everybody raves about the mackie 1204 mixer's preamps and the extra channels give you some options down the road. If thats a little out of your price range, check out some of the smaller preamps. I hear good things about the presonus blue tube. Some people like the Art tube mp but i just got one for christmas and don't care to much for the vocal coloration. There are a lot of choices for preamps under $100 bucks but try them out first.
I have been using a sm57 straight in up until i got my condenser and preamp. as for the inputs beirg TRS type. I dont know . sounds right though.
