I want to do something to improve my current lousy UPnP setup, and I'm looking for advice from those who have been down this route...

It appears to me that both the server(s) and client are poorly designed.

I have two NAS's. The first is a 1TB (mirrored raid) Linksys NMH410. It came with some kind of UPnP server of very limited capability... This has (in addition to my photo library, which is not there to share, just to store) my old AAC Itunes library, which will some day be phased out, when I get everything re-ripped, but which I want access to via UPnP for now. Ripping originally done by Winamp, many bad rips, pretty accurate metadata, OK for Ipod, not good enough for my main listening setup

The second (newer) one is a QNAP TS669PRO, raid 6. I have currently installed Music Station, Plex Media Server and Twonkey Media UPnP servers, none of which are very satisfactory. In addition to other stuff, I have a directory which I am ripping FLAC to, for listening at home, and a second directory which I am simultaneously ripping AAC to, eventually to replace the Ipod directory on the Linksys when I get everything re-ripped. I am using the dBpoweramp CD ripper and (as appropriate) the Music Converter to populate these directories. For now, I want the UPnP to access the Linksys Itunes directory and the QNAP FLAC directory. After I re-rip everything, I'll access only the FLAC and probably a small directory of compressed material that I only have MP3 or AAC copies of. I also may want it to access one or more directories of .WAV files of material I am recording/editing for myself or others.

Right now my main listening area is fed by a Yamaha RX-V475 receiver which has a built in UPnP client, which is miserable. It does not display album art on the TV, and as I recall, you can't select which directories you want to look at, and searching a large directory with the remote control is an exercise in frustration. I also have a Samsung 80-F7500 Blu-Ray player with a UPnP client. A little better than the Yamaha, it does display album art for a couple of minutes not very big and I think only the front cover? Searching is as miserable as the Yamaha. Also it takes a long time after you have turned it on before it has collected the directory information to display and allow you to make a selection. Both devices are connected by 100baseT Ethernet to my otherwise gigabit network. The TV is a non-Ethernet Samsung. The speakers are good, actually made for small professional studios.

Eventually, I want to add a second listening area, with its own setup. I have an old stereo amplifier I intend to use for that.

So first the UPnP server? I like the description of Asset, but should I wait for the QNAP release, try the QNAP beta, or get a Rasberry Pi?

Now what about a client? I have loads of extra inputs on the Yamaha, so something stand-alone, plugged into either HTML or composite and analog audio would make sense. I assume there is no way to upgrade the clients in the receiver or BluRay. Then there is the issue of how to control it? I could use a wireless mouse and/or keyboard if the client could be controlled by that. A really neat client would be able to be controlled by a smart phone or tablet, in my case Android, by WiFi. Trying to use a TV style remote is an exercise in frustration if you have a decent size library. There has been some mention of an Asset client, but I don't see it anywhere on the website, certainly it isn't listed for purchase, unless it comes with the server, and then the question is what operating system does it use and how do you control it?

Any suggestions on what flavor server to go with and what to use for a good client that would properly display album art, be stable and reasonably responsive to commands (and sound decent) and allow easy selection of items to play?