Lots of remotes can do this. A remote with volume punch through capability will adjust the receiver volume regardless of the device mode it is in. Switching to the desired input on the receiver is done by assigning macros which switch device modes, and send the appropriate discrete input commands.

Actually your Comcast remote is quite capable of doing all of this, and if you want to set it up, I'll make suggestions on how to do it. (But I need to know the actual model numbers of your equipment-- rc-682m is the model of the remote, not the Onkyo receiver model. And Samsung has used more than one IR scheme for their DVD players, and yet another for BluRay.)

Some people like the Logitech Harmony remotes, which have the concept of activities like Watch TV. Of course these are also really just macros. The Sony RM-VLZ620 is another possibility.

Or are you anxious to spend $200 on a flashy remote? The URC R40 seems to get good comments on this site.