Hi Superdan,
No, it's not necessary to use an electrostatic center channel speaker; indeed, it might work against intelligibility--if the center was a dipole design--if you did.
I know the Martin-Logan Aerius. A neutral wide-range dynamic center-channel speaker like the Axiom VP-150 should be a reasonable timbral match with the Aerius mains.
Since you like dipole main speakers, I've selected 4 quadpolar Axiom QS-8 surround speakers, and the EP-350 subwoofer to complete the system.
As to your alternatives in the HT electronics, it' rather six of one and a half-dozen of the other. I'm all for convenience in HT operation, so I'd likely opt for the Denon AVR-3802. Bulletproof amps, etc. But only you can really make that choice. . .Perhaps other visitors to our message boards will have some opinions.
Regards,
