[marcan]

Thanks everyone for the comments. This certainly clarifies a lot of the details about the OI.

Right now, I'm considering two options: a 100K digipot in rheostat mode (the "hack") or the 10+1K divider. I'll probably end up trying both, and see how they behave.

On the subject of DACs and op-amps (or op-amps with the digipots), how would you deal with the range limitations of the op-amp? Even rail-to-rail op-amps aren't truly rail-to-rail (they just get close). Would you be able to use the full input range using an op-amp?

As for the +5V Aux supply, I'm pretty sure it'll meet my needs, based on Dave's info and my own testing, as far as the power required goes. A more important aspect is how the voltage drop due to the current limitation affects the analog inputs when the current is higher and the voltage drops. I'll do some testing once the components arrive.