Upgrading from RPi2 to full blown "NAS"

I am currently using a Raspberry Pi 2 as a very basic NAS/Media Server/Usenet Downloader set up. I just have it set up as a SMB share with NABGet, CouchPotato, and Sonarr scripts running. I have 2 External HDD hooked up to it, a 5TB Seagate Expansion, and a 2TB WD Passport. I use other Raspberry Pi 2's as my frontends loaded with OpenElec.

My current set up works pretty well for my needs, but my biggest concerns are the limited bandwidth of the Raspberry Pi 2 being that its 10/100 and shares with USB, and am also iffy with having my media on external HDD's that are obviously not made for 24/7 use. I also sometimes, albeit rarely get buffering issues when serving up some of my higher quality files.

I want to stress that my build is not going to be holding any sort of critical data, I also am not going to be backing up any of my local machines to this. Obviously losing a 4TB of media would suck, but it can be replaced. I'm just looking to lessen the chance of that happening and also looking for a cleaner build all contained within a single box. All this build needs to do is be able to serve up my media, as well as be able to run NZBGet, Sonarr, and CouchPotato.

Here is a build I have put together:

PCPartPicker part list / Price breakdown by merchant

CPU: AMD 5350 2.05Ghz Quad-Core Processor ($45.99 @ SuperBiiz)
Motherboard: ASRock AM1H-ITX Mini ITX AM1 Motherboard ($49.99 @ SuperBiiz)
Memory: Kingston HyperX Fury White 4GB (1 x 4GB) DDR3-1866 Memory ($19.99 @ SuperBiiz)
Storage: A-Data Premier Pro SP600 64GB 2.5" Solid State Drive ($34.99 @ Newegg)
Storage: Western Digital Red 4TB 3.5" 5900RPM Internal Hard Drive ($149.00 @ B&H)
Storage: Western Digital Red 4TB 3.5" 5900RPM Internal Hard Drive ($149.00 @ B&H)
Case: Fractal Design Node 304 Mini ITX Tower Case ($68.99 @ SuperBiiz)
Power Supply: SeaSonic 360W 80+ Gold Certified ATX Power Supply ($57.99 @ SuperBiiz)
Total: $575.94
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-12-15 16:11 EST-0500

Will this be able to pull the weight for what I need to do? Also would it be possible for me to load Kodi on this box for my living room HTPC, as opposed to having this box plus a raspberry pi 2 in my cabinet.

Any and all feedback would be greatly appreciated as this is definitely new territory for me. Thanks in advance!

Yeah, I just figured it would be bonus points to use it as a HTPC also, but yeah, the PI's have served me great so far.

Is loading NZBGet, Couchpotato and Sonarr beside OMV very dificult? If I've read correctly OMV is just loaded over Debian Wheezy yes?