Sure, you can turn the wireless function of the Time Capsule off if you do not need for it to act as a wireless router. Then, it becomes a simple backup device that connects to your main router via an Ethernet cable. Configure the TC in Bridge Mode for this.
Your Mac will be able to backup over the wireless network or directly via an Ethernet cable. Just think of it as a hard drive that is connected to your main wireless router.
I guess what I'm asking is this: Is there an ability to disable the "AirPort Base Station" function of Time Capsule and instead utilize one's own router for wireless connectivity (and subsequently, AirPlay) while still wirelessly backing-up my Mac device to Time Capsule? I hope that makes sense.
You can do this.. as long as the TC is plugged into the router doing airplay.. airport extreme or express. And put TC in bridge.
I have a Time Capsule as the primary base station. I wanted to allow AirPlay from any device so I bought an AppleTV but realized that my Sony receiver does not play digital audio from HDMI to the second zone amp. After searching online for a solution, I purchased an AirPort Express to connect the mini audio port/optical port to an available audio in port on my receiver.
When setting up the AirPort Express, I assumed incorrectly that I wanted to "extend" my Time Capsule network. This allowed my AirPort Express to access AirPlay streaming but it frequently stuttered and stopped/started and it was VERY frustrating.
After searching here for a solution, I realized I need to configure the AirPort Express to be a "client" of the Time Capsule, not "extend" it. In the AirPort utility I changed the option to "Join a wireless network".
This article http://support.apple.com/kb/HT4587?viewlocale=en_US&locale=en_US explains why.
After changing to client mode, I no longer have streaming issues. Now the entire house can use the Apple Remote and vote on songs using the iTunes DJ playlist. Audio/Geek nirvana.