I don't think you would want to go with a 37C. It is probably not even close to a timbre (or "voice") match to the Athenas. You will not have a smooth sound transition to match the movement on the TV screen. Sometimes you can help this problem a little by moving the center forward and back, but it won;t correct a major mismatch.
The 37C is also one big, heavy piece of equipment. Putting nearly 35 pounds on top of your TV may be a serious problem for the TV. Most aren;t designed to take that kind of load for long. It's also a very big box that may have very low WAF.
I would recommend you go with the Athenas. The specs on their center look very good. It is better than the 37C in the aspects that I have mentioned. It's much lighter, physically smaller, and matches the speakers you already have.
Just don't set the receiver to "large" for the center and you should be fine. Setting the center to "small" sends the low frequency signals to your mains, that will be much better able to take it than your center. Signals that low are pretty much omnidirectional anyway (at least for human ears), so there is no need to have them flow with motion. The mid and treble are much more of a pinpoint source and are what drive the motion and locationof the sound. The Athena center is certainly equipped to handle those frequencies.
Both my HT systems are Infinity-based. If anyone would be recommending them, it would be me. In this case, I'd have to say no.