Hi Eric, I've been learning all this as I go over the last week ... I've probably literally spent about 40 hours this past week just learning all this stuff. That said, my needs are not quite your mom's.
GPU: Based on everything I've been able to tell (from
my thread on the ArcGIS forum to my less than fruitful conversation with one of their techs), Arc will NOT use the GPU much UNLESS you (your mom) is doing the 3-D analysis stuff. I don't -- I just draw on the maps pretty much, all 2-D. All my 3-D stuff is code I wrote in another software program that also doesn't use the GPU much.
RAM: You don't need to go the way I'm going with RAM. I think most people these days are more than fine with 8GB, and Arc is
still 32-bit so can only make use of 4GB RAM. I'm going with 64GB due to other, custom, software.
CPU/Motherboard: With that in mind, your mom may be able to go with the cheaper LGA1155 sockets, so something like the Intel i7-2600K chip and a supporting motherboard. The 1155 socket motherboards are around $100 cheaper for the same features as on a 2011 (other than the quad-channel memory and up to 64GB RAM).
That said, I'm likely going to order today. If you PM me with an e-mail address, I can send you all the information and justification on the parts for the final build I'm doing. With scrimping and limited-time coupons, I'm getting in at about $1950 (without monitor, keyboard, mouse, speakers).