GC, welcome. Yes, the EP350 does have a balanced input, despite the spec list, but as was mentioned, it's not relevant to your use, because your 2235 doesn't have a balanced output. The sending unit has to send out two voltages(rather than one)on the two wires of the balanced cable, with one voltage reversed 180 degrees in polarity. Then, the receiving unit with balanced input circuitry "re-reverses" the voltages so that any noise that came in on the two wires tends to be cancelled out. This generally isn't needed in home environments where the interference levels aren't unusually high.
Some misconceptions as to terminology and technology have come up here. Subs don't have "internal crossovers"(even if that label is used), but only a low-pass filter which rolls off the sub driver, but has no effect on the speakers, even if they're connected through the sub. A crossover has to both roll off the low frequencies above the set frequency and roll off the higher frequencies below that same point.
Since you have no crossover circuitry in either your receiver or speakers or sub, your M3s will continue to run full-range(down to their limit of 50Hz or so), while setting the EP350 low-pass filter to 80Hz, will roll the sub off above 80Hz. Not a perfect blend, but not bad, although the M3s aren't relieved of the low bass burden as they would be with an 80Hz crossover set in an HT receiver's bass management.
If you're thinking of combining the two outputs of your 2235 into one with a Y-adaptor and feeding it in to the single sub input, no that isn't a safe procedure. Using a Y to split one voltage into two is fine, but using it to combine two voltages into one isn't. The voltage on one branch doesn't know that it's supposed to only go into the sub and so it also runs up the other branch into the other output, causing distortion and possible damage. The simplest procedure would be to just connect with speaker wire to the speaker level inputs on the sub.
If you have any further questions on this, don't hesitate to ask.
