I think the main things you'll be losing are:

1. Digital inputs (not counting USB)
2. Sub Input.
3. Video switching.

So as long as you are fine with your TV doing all the video switching and all you components can output full range, analog stereo outputs you should be fine. The bluray probably wants to output 2.1 at worse so you may have problems there.

Never heard the NR1602 but I have an RR2150 and it can rock the house.

Note that your Marantz also has room correction software. You didn't say if you were using this with you two channel setup though. The 2150 doesn't have room correction.