I should have made her a tiny little PC like Ian's most recent build lol.
Spearheading the mini-ITX revolution since 2016.
In all seriousness, mini-ITX is fantastic for some use cases, but it is definitely harder to find parts to support it if you're in the AMD camp. While there is a reasonable selection when it comes to Intel (33 new mobos), there are only 8 AMD boards, with only 4 of them supporting FM2+. The number of boards with AM3/AM3+ support? Zero.
You would have definitely had to buy a new CPU/mobo. The case would definitely been cheaper, but the cost of those parts would have more than made up for it.
I'm thinking there just isn't enough demand for more specialized AMD builds, which is a shame. The A10-7800, even with the AMD stock cooler (which, from what I read, are quite bad...not sure if things improved over the last few years) runs pretty cool, even under heavy load.
Another tricky aspect is the PSU. If the mini-ITX case you get supports an ATX power supply (like mine does) you pretty much need to get a modular PSU. Even with a modular PSU, you end up with a bit of a cabling disaster. If it weren't for the PSU, my build would be very clean. However, as a result of that (plus the fact that I need to use both SATA-style and Molex-style power connectors for the HDD and front fans, respectively), there's a bunch of slop in the front of the case that I had to zip-tie away from the fans. Yuck. I've considered just using the Molex cable and running a Molex to SATA adapter to my HDD to simplify the wiring a bit.
If you get a case that uses a mini-ITX PSU, you've traded wiring headaches for a whole different set of much larger issues. On Newegg, the highest output mini-ITX PSU puts out 400W. However, none of the units that put out that kind of wattage are from brands that I would trust using for a new build.
What it really comes down to is that you're really not saving much space if you do a build like mine (mini-ITX + ATX PSU). My rig is a bit shorter than a mid-tower but is a bit fatter since the mobo sits flat. If I didn't get the case for $40 I wouldn't have bothered.