osquest

Personally I don't see having much to back up directly from the Surface RT. Office docs will be in Skydrive and I'll use Skydrive for any other app that can use it. Apps will be in the MS store. Only gap I see is apps that only have local data without a cloud component. Plus it would be good to be able to backup settings.

I have the 212j and find it to be fine for time machine and other backups and think you'll find it fine as a file destination. I also have a 212+ and do find the added memory and cpu are noticeably better when running apps.I mainly run photo station and find thumbnail creation and the responsiveness to be better. Synology benchmarks the + disk to be faster. I've never benchmarked them myself but I'm not frustrated by files copies even when apps are running. Just in use, they seem comparable for my usage which is pretty light. Just backups and file copies, no video streaming or actively editing files on the NAS. The + model also has some additional features which may or may not be important and may have different external ports. My 212+ adds USB 3 and the ability to automatically copy from a USB drive or SD card to the NAS

I started with the 'j' to see if I liked it. Like you said, it's the low-cost way in. I upgraded to the '+' for USB 3 and the better hardware for apps. Considering how long ago I got my 212j (Nov 2011) and that they've started release the '13 models the 212j may be due for an upgrade and I would guess it would get USB3 (but it's just a guess)

I use Crashplan for a couple remote PCs, in addition to on my own WHS. One feature I like about it is that it emails me if there's no backup in the last two days (think this requires the paid account and backup to their cloud). Also sends a weekly report of backup status so I know things are working without have to remote into the PC. Recommended as a data-only offsite backup solution.

Synology is out with your combined requirements. Synology Hybrid Raid will give you #1 but not #3. It's basically the same as Drobo.

I love these drives and they were what I was buying before the prices sky rocketed. Cool, quiet and problem free. Running 8 of them.