Have you seen this UAD DSP chart?
I have an Apollo Twin Duo but have never used it to profile an amp because I’ve read that the plugins don’t translate very well when profiled. If I were to use it to profile, I’d probably only use a preamp/eq plugin like the Neve 1073. From the chart above, that would take up 40% of one of the two chips on my Duo so that would be more than enough for 2 mic’s. You could even add a couple of 1176 comps to both mic’s and still have some DSP left.