I missed this part:
"Ideally, whatever I get should work with the case when I am working 1-on-1 with a live drummer and Biab is playing bass."
In that case, I would agree with Eddie:
"For live PA applications, you would be best served to buy the biggest amplifier you can."
We run 600 watts at 4 ohms through two Yammy S115V's just for vocals and backing tracks, and we're just a duo!
Regards,
Bob