ShieldTV external drive or NAS

What would be best to purchase a external drive compatible with ShieldTV and use the shield as DVR server or a NAS device compatible with channels? And what one depending on your selection.

I currently have a NAS device but it is not compatible with channels (not powerful enough, but will work okay with HDHR on it) and it won't Mount to my shield via USB. I have a WD cloud device and I guess the USB on it is only to mount other drives not to mount to PC. I have it connected to network via Ethernet and mounted to Shield that way but that doesn't help me.

Current channels server is on surface pro 3 hardwired but I want that to be portable and right now it is not with current hookup.