Well after showing off my new system (that many in this forum have assisted me with) to my in-laws I got tasked with building one for the dreaded "Mother in-law"!!! Yes thats correct, you read it right. The ultimate test, should I build one that works or one that every time she hits the power on switch 115 v's shoot through her finger and out her glaring eye's!!! Seriously tho, the father in-law wants one built for her for an X-mas gift. A very inexoensive one based on an AMD 939 CPU platform. I built mine on around the E6600, so I know even less then before about an AMD set up. But this is what I have so far, and please remember this is a very very budget centered system mostly used for brought home work and some gaming. Please look at the following and give you recommendations.
XION XION _ Solaris XON-409 Silver Steel ATX Mid Tower Computer Case - Retail
I looked at that case you chose and then looked back to make sure you were buying that for your mother-in-law. She might have different taste than mine, but that case is more like something I'd by for my nephew.
You didn't mention what your budget range was which is always helpful.
And I have to admit I agree with the others that recommend a pre-built Dell (or HP) system. For about $480 you can get an AMD system with 17" LCD that has a free upgrade to Vista. Depending on what games are involved you'd want to upgrade the video system.
On the whole I think your in-laws would consider the Dell a "quality" product based on the advertising they do. Even with the warranty and support through Dell they'll still be after you for tech support - so count on that.