NAS or HDD Dock?

Right now, all of my images fit on a 1TB external hard drive. I've had the drive for about 2-3 years now and instead of waiting for it to fill up or crash (the images are backed up to a separate external drive, to Time Machine, and to CrashPlan), I'm looking at replacing/upgrading.
Currently, I'm debating between a 4-bay QNAP NAS or a 2-bay OWC Thunderbolt docking station.
If I went with the NAS, it would replace both the 1TB external drive and the "backup" external drive.
If I went with the OWC dock, one drive would replace the 1TB and the other would replace the "backup".
I would be the only person accessing the data in my house but I would like to access the images from my laptop while sitting on the couch, so I like the NAS since I wouldn't have to rely on leaving my iMac up and running.
Whichever device I go with, it would also be storing my iTunes library and I would like to be able to access my music and movies from my AppleTV.

It sounds as if you have reached a decision, that you need NAS in order to provide data access to your laptop even when your desktop PC is off/asleep. What's your question?

BTW, an NAS configured as RAID1 provides 'data redundancy' via its mirrored data...it does not provide a 'backup'...a fire could destroy the RAID unit and leave you with nothing.

Also, if the RAID 1 controller itself fails, you may be in trouble as the controller is what codes the disks. You may not be able to simply remove the drives and mount them in another RAID 1 controller. When a RAID config is written to disks, usually it can only be mounted by RAID controllers in the same family. (i.e. I have read that a RAID array created on a PERC controller wouldn't be readable by a Smart Array controller).

I'm not totally against leaving the iMac up and running. With my Mac mini, I used to leave it up and running all the time and access the external hard drives over the network.
It seems I'm able to get more storage for less $ (to an extent) with the dock. Also I'm not sure if my AppleTV will be able to grab the music/movies from the NAS without my iMac being awake.
Also, if anyone has any experience with either device, it would be helpful.

Itunes home sharing for video won't work without the iMac being on unfortunately. A NAS with a built in iTunes server will stream music however. I have the same issue and because I stream a lot of video from iTunes to Apple TV and iPads, I'm forced to have a computer on.
I've just gotten an old laptop and loaded up windows on it with the purpose of making it an iTunes server. Lower power consumption, built in battery backup, and I have my choice of drawing media from the NAS or an attached external drive. Hopefully it works.
I currently try have a 4 Bay NAS as well as a few hard drive docks and a couple of externals. I like the redundancy of the NAS but the speed of the USB 3.0 is very nice.