"Reusing" is good. My first experiments with OMV started with a Raspberry PI that I wasn't using, an 8GB SD card, and a used 1TB drive that was laying around. Now, with a 4TB drive for data, that experiment evolved into a full server and data backup.
On the other hand, like you, I needed a 1G network interface mostly for imagining clients. The PI will do it, but at 100mbs it's too slow to do more than one client at time. (And even at that, it's still like watching grass grow.) The PI will serve files just fine, but it's limited beyond that particular function.
I'm building an i3 server right now. Man, so far, this rig is flying! When one is used to an R-PI, an i3 with 12GB ram feels like WARP speed.
I know. When I was first looking at using OMV I used an old, power-hungry Dell tower that ended up dying in the middle of my testing. I wasn't going to use that machine anyway, but it was a good way to test. After that, I bought a Raspberry Pi specifically for OMV. I used it that way for about 6 months before deciding that I wanted to use something that can handle faster network speeds, so I replaced it with an old HTPC that I thought had died, but as it turns out, it only had a dead drive. I put the hard drive from a PC that I had upgraded to an SSD in its place, and that's how I've been running my setup for a few months now.
