Did you ever consider moving your equipment to one of the side walls near your speakers? You can run your cables behind your baseboard trim. And you should be able to fish the Atmos stuff up the walls from the floor up also. But you sure do have long runs from where you are located with your equipment.
Unfortunately that was never in the plan. Nothing is painted yet (just tape, float and texture), so ripping things apart is on the table, just not desirable. I had a dedicated 20A circuit installed in that cubby specifically for the equipment, and I already ran the HDMI and CAT6 from there to the projector.
My thought was that if it becomes a problem I would combine the pair of 16AWG wires at both ends since I plan to amp the front channel anyway (pre-amp out of the receiver). My receiver is an 11 channel, but only 9 of them are amplified. So I'd run direct from the receiver to the Atmos and surrounds, and then pre-amp to a three or five channel amplifier for the front.
EDIT: Wait! What if I were to pre-amp to those long runs, and then amp them at the front of the room?