Now that the Sia network is up and running even though it's a closed beta you could narrow down some specs for future Sia mining rigs.
There should be a whole section about sia storage rigs.
I think our POW algorithm is going to be blake2, but I wouldn't buy any asics/gpus yet. As for storage rigs, we should probably create a forum that we open alongside the open beta. I've seen on the storj irc that you can get large rigs for around $46/TB, but I think that those rigs are actually designed to be much higher tolerance than you need on Sia. You might be able to push the price closer to $35 or $40 per TB.