Modem/Router Combo

Unfortunately, you cannot use an Apple Time Capsule as a cable modem.

As far as a recommendation goes, unless you can find some kind of 3-way hybrid between a router, cable modem, and storage system, you're pretty much out of luck. I'd stick with your current system.

Sorry, I do not understand whether you want to replace the Time Capsule with a modem/router....and give up your current backup ability with the Time Capsule hard drive.

Or

Whether you want to replace the modem with a modem/router. If that might be the case, then you would not need the routing capabilities of the Time Capsule, but you might be able to use it only as a backup device. This would not really "declutter" anything.....since you would still have 2 devices.....a modem/router and a Time Capsule.

And, you might not have thought about that fact that Apple does not officially support Time Machine backups using a third party router, if you intend to keep the Time Capsule.

If you really are looking for only a modem/router, I doubt that you will find one with a built in hard drive. But, the first place to start would be to find out which models your current Internet Service Provider supports. Once you have that list, post back with that information and ask other users to comment on their experience with one of the models on the approved list.