I think you'd be fine with 80Hz. I use a more complicated setup with my HT receiver and M80s, but for just plain stereo, you'll be fine with 80.

Yes, the EP350 has balanced inputs and outputs.

The 1/4" phone input is, I believe, not balanced, but is there to be adapted to the unbalanced RCA input. I didn't think 2235B had balanced outputs, so there we are.

I am the Doctor, and THIS... is my SPOON!