Hey munkyman,
The vSphere Storage Appliance was created for the small to medium business market or for branch offices, where it would allow you to have a small 2-3 host cluster. The Storage Appliance works very much the same way VSAN does in some aspects where it just takes the local storage on the Storage Appliance and creates a Datastore out of it which is accessible to the hosts, typically through iSCSI. Once you have that in place you would be able to take advantage of HA, vMotion ect. However when we looked into the Storage Appliance a few years back the price tag on it was roughly the same cost as a entry level SAN. So in most cases we opted out on it as a solution. You may want to see if VMware has changed there pricing on it to make it more desirable as a small implementation solution.
There is a lot of nice little NAS boxes out there that you can get, I see Synology boxes a fair bit in lab enviroments, however I haven't looked into them in a great detail for production purposes. The most important thing about a NAS box is that it is on the VMware Hardware Compatibility list and meets your Storage IO requirements. I like Netapp's entry level boxes as they give you the full gambit of options, however they come at a little higher of a price tag.
VSAN you would need additional hosts a min of 3 I believe and it takes all the local storage and turns it into a virtual storage pool which all your ESXi hosts can access. I'm not sure this would be the best fit for you as I don't think you would want your hosts as vSAN's and ESXi hosts. So unless you have 3 other servers kicking around and want to buy additional licensing this probably isn't the best route.
I hope this has helped.
