Can I stream from my nas to the hi fi using apple tv or is it just to stream my i tunes library?Or what other device can I use as a streamer from a nas, not too expensive and apart from squeezebox?
Cambridge Audios NP30 Streamer could fit the bill & is good fer 'High Rez' too @ up to 24bit/96khz IIRC. I've recently bought its bigger Bro' the SM6 & have been very impressed. The SQ is simply superb & its a good deal better than my previous SBT + MF M1 Dac. The NP30 should have the potential to be at least this good with a future Dac upgrade & straight outta the box I'd have thought it would have a fair chance of being even better than an SBT sans Dac, as C.A. have far more know-how re implementing Hi-Fi quality analogue output stages + a good deal more experience with digital audio too than Logitech.
C.A.'s NP30 is currently on @ £250 from Richer Sounds which is VGFM as before the SM6 replaced it it was over £400. Another Option worth mulling on is a NAS upgrade instead......mad as that may sound......bear with me.

Synology NAS enclosures can output 'Bit-Perfect file based audio @ up to 24bit/96khz using their Audio Station S/W + be controlled from a smart-phone/tablet & will also give you access to internet radio etc. They're really quiet so not at all intrusive & you could easily just repopulate one of these with your existing drive/s.
I've discussed this in a couple of recent threads.....Food fer thought?? I actually think the little lash up I discuss in the thread sounds even better than my previous SBT in the bedroom setup.....all you'd need would be a suitable USB Dac that works with native/pre-installed Linux USB Audio drivers & you'd be up & running with a neat solution that does a lot more besides. The Synology DS213J would be likely more than good enough & costs around £170.
See this thread fer more details>>>
http://www.hifiwigwam.com/showthread.php?88255-Upgrading-to-a-better-Nas-with-more-storage
Of course upgrading to one of these NAS's would also give you some interesting multi room opportunities if you got a streamer as well. One caveat I'd add is dependent on which NAS you're currently running is that C.A.'s NP30 does run on UPnP/DLNA for streaming & my old Netgear ReadyNas Duo wasn't very good running this as I've since discovered that UPnP servers need a lot more processing power to work well, whereas SBT running off LMS really doesn't & will work superbly with relatively low powered NAS's.
Sooo if this is the case for you, but you still fancy t' NP30 I'd consider streaming from your full fat pooter/lappy instead.....at least as a stopgap. Also if considering this & wanting to do it in a couple of steps i.e NP30 first then NAS then the full fat DS213 could be a better bet than the 213J due to considerably more powerful processor. TBH I'm not really sure at which point the increased demands of running UPnP/DLNA is met in terms of processing power.....So perhaps some research on t' Synology Forum or I know there are a couple of NP30 users here too as well as the SM6 so someone should know.