USB drive vs NAS for storage/streaming/back-up

Is there any sonic benefit for a NAS over a USB drive for storage and streaming? I'm using a 1TB USB drive for streaming FLAC files through a Sonos (Cullen modified) to a DAC. Sounds good. I was planning on getting a NAS, but I could just as easily get another USB drive and back up maunually when needed, not a big deal. USB drive is quiet, easy to use and situate, seems to work well. Why go NAS? Ethernet benefits? Sonics? Thanks for any input.
With a NAS drive you won't need to keep your computer on. Don't get an NDAS drive - that WILL require your computer to be on.

That is why you want/need an NAS drive.

I am am also using a Cullen modified Sonos ZP-80. I use a Buffalo Teraserver NAS drive, attached to my half wired/half wireless network. Like Stevenstone said, your PC does not have to remain on with an NAS device, only the hub or switch needs to remain powered up. Some of my Sonos units are hardwired and others are not. I've not been able to tell a sonic diference between the wired and wireless connections. The Teraserver is RAID 5 configured right out of the box, so the data recording is already redundant, not really requiring any other backup.
Thsalmon: Thanks. I'll investigate NAS units. Need something quiet and cool running that can be in the listening area. As I have a USB drive, don't really need RAID. I'm also running wired and wireless with the Sonos.
With NAS drives, you can attache them to any of your Sonos units via their Ethernet connections, but I STRONGLY recommend putting your NAS drive in a separate room from your listening room. Many NAS drives have fans and do generate some amount of noise. Attaching them to your wired hub is the usual integration method.
Stevenstone is right - get the computer hardware out of your listening room. Assuming you have your wireless router in a closet somewhere, get a cheap NAS and put it in there with it (I spent all of $225 on mine).

One of the main benefits of Sonos is that all the "work" of de-compressing the file and turning it into a digital stream is done in the Sonos box itself. Since file transferring across even the cheapest network device already has more error correction than the best CD transport, you don't have to spend a lot on this. Buy cheap and spend the saved money on a backup drive (or a nicer DAC!).

Additional tweak to your Cullen modded Sonos; get a decent power cable such as the PS Audio Power Punch and you will see further elimination of the grainyness of the Sonos digital out as well as increased dynamics across the board typical in a power cord update.
Good suggestions. Ordered the power cord. As another sonos user with the mod, do you know if they plan on supporting 24/96 in the future? Or improve the software for managing large collections, allow metadata, etc. The basic sonos platform has great potential and is very stable, but it does'nt seem they're really committed to supporting the audiophile market (which is admittedly small).
the scuttle I hear on the sonos message boards is support for volume normalization metadata standards (there are 2 competing standards) and possible multiple library support (i.e. you could have a "classical" library, a "jazz" library, etc). They don't talk about any plans themselves, these are all speculation on the part of users supposedly "in the know" - for whatever that is worth.

Given their latest modifications were almost strictly aimed at the computer/wi-fi side of things, I'm guessing they aren't too concerned with the audiophile grumblings for high resolution and better clock circuitry. Their business model doesn't really cater too much to our needs, but the library size thing should be a universal problem that gets addressed. The other thing I would look for is a new controller that looks & acts like the iTouch/iPhone model.

Long term, I'm hoping one (several?) of the higher end equipment manufacturers like PS Audio will pick up on the Sonos delivery model and offer a product engineered towards us.
Over the last week, I have hooked up a Cullen modded SONOS ZP90 and Bridge, and yesterday added a ReadyNV+ NAS. The DAC ia a Northstar 192 into a Dodd preamp, Pass Aleph J amp, and Merlin TSM-MMe speakers. The NAS holds my 50GB iTunes library, and the system is wireless controlled by my PC or my iTouch.

I have not done a careful A/B test, but on first blush, this system sounds great, as good or better than my MF A5 or Marantz SA11S1 CDP's. As a bonus the SONOS internet radio offers hundreds of world-wide stations with few if any drop-outs. That radio sound is very good (I listen to classical and jazz.)

An important feature for me with the NAS is RAID-5 which pretty much guarantees it will save stored data in a crash. Having the experience of losing stored back-ups years ago, I do not want that to happen again.

I am really impressed by the quality of the sonics and the convenience of the SONOS system. Looks like my CD collection is bound for the attic.

Sonos offers plug-in (from Apple application downloads - free) to control the system with your iPhone or iTouch.
Very cool.

I own Sonos system as well as MacBook Air which is my reference source feeding RWA Isabella preamp with Isabellina NOS (USB) DAC. iTouch controls it all flawlessly.

NAS LaCie 1T drive stores the library for both - Sonos & MacBook.

Glenn says that his Cullen modded Sonos sounds unmodded Sonos is so-so in comparison to my MacBook or Consonance Droplet CDP.

I am still sailing through options for my Sonos - Cullen mods are the most aggressively that might be the next step.