re: Release of Steam Machines/boxes?

It's not really about what's "safe" to order, but rather which brand/model you should order at any particular moment. For example, I picked that ASUS GTX 760 because it was the cheapest 760 at the moment that uses an aftermarket cooler. That's still the case at the moment, but I have no way of knowing if (a) Another model of the 760 will go down in price and beat the ASUS, (b) the ASUS model will go down, (c) the ASUS model will go up but still be the cheapest of the bunch, etc.

This goes for most of the parts. For example, this RAM is faster and cheaper than the RAM I put in the initial part list: LINK

but tomorrow it might be a different kit that's cheaper. RAM is like a commodity. I remember paying less than $40 a year ago for the same kits that are now $80. Just how it goes.

The parts that are less likely to shift in price significantly enough to warrant a brand change include: Motherboard, Hyper 212 EVO cooler, Case, and hard drive (that hard drive has been $60 for ages. Also, if you wanted more storage space, another $28 will get you a 2TB Seagate: LINK )