Using an NAD AV receiver as a preamp? for now

My 12 year old NAD 1600 Preamp/Tuner is starting to go south. I need a new preamp but I was thinking that I might go home theater... but still try to keep driving my front stereo channels with my tube amplifier.

In other words, I would like to integrate a decent analog stereo system into a home theater setup. Is this a good idea?

So, I would use the new NAD AV receiver as a preamp, then when I go full home theater, have the receiever drive the remaining three channels. I still listen to mostly stereo but from time to time it would be nice to watch movies in 5.1 in the existing system. Is this a good idea? Any other reccomendations?

The T753 is teh first ste-up in the current line.
It gives you a high degree of flexibility and doesn't cost a fortune. The "main-in/pre-out" feature for all six powered channels (and decoding for the sventh) will let you use it simply as a pre/pro while using the other six amplified channels for second zone/distributed audio applications if you choose.
This is not really audiophile stuff but a reasonable compromise.
NAD never has the latest video switching but with macro enabled remotes and the video switching ability of most TV's this is not often an issue.

Good luck!