Is there a digital audio switch out that is good quality and can possibly be operated via remote so I can still seamlessly use my Harmony?

I have 2 optical and 2 coaxial, and they are all full. I am trying to avoid the optical input on the front of the receiver purely for aesthetic purposes.

Receiver: Pioneer VSX-815

it's kinda pricey just for adding one more digital audio input with the convenience of harmony remote programmability.... almost makes you weigh what your receiver upgrade options are.
<a href="http://www.gefen.com/kvm/htswitchers.jsp">Gefen home theather switchers</a>

Polk XM XRT12 XM Reference receiver
Comcast HD/DVR box...not sure of model number
Toshiba HD A2
Xbox 360
Oppo 980H

I'm a little confused as it appears as though you have everything you need already (four components and four digital inputs), but I'm figuring you have another source to hook up on top of what you have listed.

If this is the case, all you need to do is hook up your Oppo to the receiver using the (somewhat separated) 6 ch. inputs instead of the optical or coaxial cable, which will leave you with a spare digital input.

If you are connecting a BluRay player (needs to have a built-in TrueHD/DTS-HD decoder as your receiver doesn't), hook the BluRay to your receiver with the 6 ch. connections instead. And then re-connect the Oppo with the digital connection.

Given how limited the sound quality is with XM I'd suggest using 2 channel analog connections instead of a digital connection.

With 6 channel audio from the Oppo you can expect very impressive results as the Oppo has a very useful D/A convertor with a tweak or two to enhance it's performance.
The Oppo should give you better sound than the Pioneer receiver, which won't do a great job with it's D/A convertors. Partly because they aren't great to start with and secondly because they are housed in a casing that produces lots of interference without proper isolation.

Of course, if you are not yet planning to add a BluRay player anytime soon, you can still have your XM hooked up with a digital connection, but I doubt it'll make much difference either way.

from my experience, the best XM quality is on DirecTV, followed by integrated XM tuners, followed again by the polk tuner.