1.) Better sound.
There's something wrong with your setup - the sound quality from the Receiver is absolutely superb. Other products in this space often suffer from poor analog design, but we specifically set out to differentiate ourselves in that respect.
How are you encoding your source files? If you're listening to 128K MP3 then obviously it's not going to sound that great. Quality bitrates (say, 192K or a high VBR rate) should sound excellent.
What output stage do you have? e.g. line outs into your stereo? Using the powered outputs into some speakers?
2.) DTS or other 5.1 capability!
I don't think that's particularly useful in an audio product. Even if you found an audio track with surround encoding (most tracks are not surround encoded - any surround effect is coincidental and not intended) it is likely that it would be lost in the MP3 encoding process.
There are digital audio formats that support more than two channels, but I'm not sure how anyone is making practical use of these at the moment.
3.) Now that you own Replay TV as well, integrate them!
We have done some work with Replay but the details have not yet been announced.
4.) [Various Rio Car suggestions]
You can already establish a wireless link to Rio Car (which has an ethernet port) although it involves a certain amount of hackery. A more consumer orientated solution is certain to appear in the future.
We are currently doing a lot of work to integrate products within the Rio range, and one possibility is for emplode (the Rio Car music management application) to include a Receiver server. Another idea, which we demonstrated at CES, was for the Rio Car to have a Receiver server (streaming via its Ethernet port).
There are also other products due out soon which tie together many of the other Rio devices.
5) Wireless in case I have to go weeding in the yard or clean the shed or play in the yard or something.
The Receiver has a standard Ethernet port - there's nothing stopping you plugging in an 802.11 bridge right now.
6) Cheaper :-)
That's always on the list, and is usually a matter of time. Right now this entire sector of technology (i.e. networked home audio) is considered an early adopter market.
Thanks for the feedback. Suggestions here and at the Rio Car BBS have more influence than you might expect.