Hi there:
I think that's the situation I'm facing at this moment too.
Someone will say 4 mics is enough, and you have no need to use 2 mics for the same amp. But is that what you want? I guess not.
You like to tweak the EQ of each mics particularly, since every mics have it's nature and it doesn't sound like the best sound if u don't eq it, when u did the eq, it's a personal setting and it represents your taste. However, ordinary mixer will provide little eq options if it's a 3 band. (much better if it's a 3 band with "sweepable" mid where u can set the start off point of the mid freq)
You will get the best result with a mixer that provide multiple out with multiple subgroup which allows u to record the sound of each mics individually for further processing. (That's what u'd like to do, right?) Also you will get a better result if the eq is more precise, so u should think about parametric eq, which let you to set the Q and the gain in terms of +/- 12 or 15dB usually. (Sometimes 17 on the quality ones)
I'm thinking about the possibility of wheter the digital mixer will do that for you.
I've posted a question up there few days ago with poor grammar, if u have the time, take a look at it.
if u like to read further about thos stuff I talked about in that post, go wo
www.soundonsound.com and use it's search function to find those reviews. You can even go to those professional shops to ask those guys for help.
Please correct me if I'm wrong. I'm a novice learner.
Kenoir