I use a Behringer 1204FX Mixer, and I think the main advantage is, it has a BUS Channel (ALT3-4). I can group a few Channels together and send them to this BUS. The Mixer has a SUB OUT which takes the signals from this "group" and sends them to my PC via the TASCAM Audio Interface. The other tracks playing in BIAB on the PC come to my TASCAM (USB) and then out (via LINE OUT) to a separate Channel on the MIXER. This way there is no feedback and I can hear BIAB and yet only record the instrument(s) I am playing...

I control the record level using the faders of the ALT3-4 Channel, and I control volume of the BIAB tracks (that I am listening to) using the Mixer's MAIN faders. The sliders/faders on the channels I have my instruments plugged into are set at the MAX level.

There's a great Website with more information about Mixers and everything else regarding recording http://www.tweakheadz.com/guide.htm and has a great section devoted to Mixers (check the Right margin) http://www.tweakheadz.com/choosing_a_mixer_p2.htm

Good Luck

2008 Gibson ES-339 Custom & 2010 Les Paul Traditional. Fender SCXD Amp
BIAB/RB 2015 UltraPAK + Ketron SD2
Windows 7/64 Intel i5 3550 PC, Tascam USB144MKII
Behringer X1204 Mixer
Bose Companion 3 and/or L1 II w/T1 + SM58 MIC