ARM-based Synos - don't bother
We have a four-year-old Synology box - it's one of the lower-range ARM-based models - and whilst it does what we need (mostly: an extra drive and a server for the Logitech Squeezebox in the lounge), to say it's hardly a speed-demon is like saying Antarctica is hardly a good location for a beach resort.
If I'd seen this story last night, I might've thought our Syno had been p0wned (sp?) for Tulipbulbcoin-mining, it was running so slowly. Turned out it was "only" indexing some photos I'd uploaded - I really should look into setting it up so it does the indexing overnight, as the Syno is effectively unusable while it devotes its resources to that titanic task. (Remember the coffee-machine on the Heart Of Gold and the Vogons attacking? Yup: same effect.)
So, prospective BitGold-miners looking to hijack our Syno for some wealth-generation on the QT: I suggest you look elsewhere. You'll be lucky to get the equivalent of a few coppers out of the old jalopy, and I'll get so honked-off at the box slowing to a crawl that I'll end up rebooting it at the first opportunity.
I think the chap down the road might have an Atom-based one, though... ;-)