Roll your own NAS

I could be wrong, but I doubt that a NAS computer needs 8GiB of system RAM. Also, I know that a NAS doesn't need a fast CPU, but you might want to shoot for something with a little more power.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...
This one is substantially faster at about the same price (cheaper if you consider shipping). If not enough, it would at least be better than the one you looked at.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...
This might be far better than even the one that I looked at and even cheaper.

The case should be fine. It shouldn't need to be great considering this machine won't have a high-power consumption CPU and very high power-consumption graphics setup. I'd get a weaker PSU because this computer shouldn't pull nearly that much wattage even at peak. Even Corsair's 430w model might be overkill.

Yeah: Between horsepower, powerdraw, and sticking to mATX, it's easy to get turned around.

I don't think I've ever seen what a Sempron draws, but if it's old like the VIA Nano, I suspect it's a little high …

The E-350 does suggest itself, but has the same "get a RAID host" issue everything else below ~20w seems to have; I found that silly C-60 looking for a better E-350 …

The sempron is an Athlon II with one core and some cache disabled. It does use more power than the other CPUs, but it's performance is far higher and power draw is still fairly low. It can also probably have the second core unlocked if the motherboard's BIOS allows it (Semprons have a roughly 100% unlock compatibility rate). At stock, the Sempron is probably a 45w TDP CPU. It probably draws around 35-40w at load.

EDIT: Athlon II x2 Regor is the die that is cut-down into the Sempron's Sargas die, to be more specific.

Change in plan:

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

http://www.microcenter.com/single_product_results.phtml...

So: Swap the mobos' around, and save~$55 converting the RAID host card to a CPU.

I could save a watt or two going to a G440, but why? It would cost more …

This leaves an open question about heat sink for the CPU, though …

The CPU should come with a heat sink.

You could do that and it should be good. Don't even both considering the G440, it is junk in comparison. The G540 is about three times faster when both cores are used and still a little more than 50% faster even in single threaded tasks. The very minimal power savings would not be worth it.

Heat Sink: I'd gotten used to the idea, already, of only the intake (that Corsair) and the PSU had fans. Minor point.

The guy(s) at Xbit seem to think the G440 should be eating the Atoms' (and the E-350s') lunch: http://www.xbitlabs.com/articles/cpu/display/celeron-g5...

The G440 is good compared to very low end CPUs. It is crap compared to even minimal CPUs for the desktops these days. Like I said, the G540 is about three times faster when both cores can be used (most software these days can use two threads, especially as far as NAS and other servers that can use pretty much any amount of cores/threads are considered).

Heat sink: http://aaawave.com/p-11818-dynatron-k618-2u-passive-cpu...

Only I've never heard of this shop; And of all the places that carry this HS, none talk about a backplate …

I don't like most passive CPU coolers. They are usually gimmicks that don't work well. I'd suggest getting a Cooler Master Hyper 212 Plus if you want an aftermarket cooler. It is very quiet and an excellent cooler despite being very cheap. Newegg has them for under $30. The Hyper 212 Evo is a little more quieter with the same cooling performance at a slightly higher price.

Also, Newegg.com and many other online retailers have the Plus and Evo.