Edit: I just reread your post and realized I totally missed a critical point: no streamer!
You can ignore everything below this edit, but I'll leave it since someone might find it useful.
I think to do what you want, you need a receiver with these capabilities. I have an Onkyo SC-PR5508 pre/pro (basically the same as the 5008 AVR without the amps). It lets you access the NAS files and plays directly (I forget which formats as I don't use that feature). You really need the TV on to navigate properly though. You can use the display on the unit, but it would be very cumbersome. I'm sure there are a number of AVRs that will do this, but I'm not familiar with which models and which have what features. It may be difficult to find an AVR with this capability that gives you a good display without the TV though.
Other options, although technically in the streamer department, is access of NAS files via a BDP. My basic Sony lets me do this (need the TV though) - higher end would be the Oppo's (don't know about display requirements).
Hope that helps a little!
Not sure I fully understand your scenario. It sounds like music only since you want to use it without TV. Or do you want music and video but a GUI separate from the TV for the music?
If music only, I would investigate the Cambridge Audio NP30 - ~ $500 (or StreamMagic 6 if you want the excellent DACMagic Plus built in to it - $1000). It is the best higher quality music streamer for the money. There is also the upcoming Olive ONE for ~500 that looks very promising. All three of these use phone/tablet GUIs. The Cambridge Audio units have a barely usable display on the unit that work in a pinch. The Olive ONE will have a color LCD display on the unit that looks to be equivalent to the phone/tablet GUI.
I have the Cambridge Audio StreamMagic 6. The app works great on iOS. It is still buggy on Android but they are actively working on that (I'm now in the beta).
If you do want video, you can actually get cheaper units that will stream music and have a tablet GUI, but the music quality will be less. Generally because of cheaper parts and because they are really made for video and music is a second consideration. The simplest way to improve sound with these is by using their digital outs into a better DAC. You can either have a standalone DAC or make sure the receiver you get has a good quality DAC in it. Another tweak is to get an improved, after market, power supply.
The Popcorn Hour 300/400 series are leading contenders for video/music streamer with tabet GUI. Dune will have phone/tablet GUI when yaDIS 3.x comes out (who knows when), but you have to be comfortable on the bleeding edge since this is add on GUI rather than from the Dune people.
I'm sure there are some other boxes that fit these criteria. Follow up if I've misunderstood or didn't address your question.Edited by pstrisik - 4/9/13 at 9:52am