hi Tim,
you could look at a 4 channel mic pre that offers an on-board mixer. for instance, i often do concert recordings with my trusty Benchmark MPS-420. it hard pans L/R pairs, so i use channels 1-2 as my main pair, then split a spot mic using a Y-cable into channels 3-4. panning is accomplished by adjusting the relative levels on channels 3-4. voila, no outboard mixer needed! in addition to the mix output, this unit also has discrete outputs, should you want to record each channel independently.
with this setup you do not need a separate mixer. personally i hate using mixers in-line when i have amazing mics setup, detailed pres and a high-res recorder.
if you're not stuck in the dark ages like me

, look at the
Benchmark Pre-420, their current unit that has pan pots (HPF, pads and solo functions too) on each channel. i'm sure there are also other pres out there that allow you to mix internally.
cheers,
-c