The M4A78 is a 790 NB board, IIRC. Should suit you well.. Never heard of the graphics card though. Good deal of a budget build.. Got some higher end ram there, so that'll eat up some funds.
Maybe a 4870 would suit you better for CAD? Never heard of the GS250, GTX series, yes. The 4870 would most likely out perform it and they can be had for a comparable price now. See if you can find yours in this link:
http://www.tech-forums.net/pc/f76/gr...e-list-212331/ I'm gonna wait till the new 5870's come down in price. Still a bit much for me seeing as I got my 4870 when it was still fresh for $190.
As far as the board, I have an M4A78 Pro sitting around, but I was never very fond of it. My Gigabyte board just *felt* faster for some reason, and it's an inferior 790gx NB. Asus boards are supposed to be really good, but I'm just off of them for a little while. The GB board never loads windows the same way twice, but the bios is GREAT!!! I HATE Award Bios in the Asus boards, but they are very consistent. Just a trade-off of what you love/hate more.
The quad cores are multitasking MONSTERS though!! If you're coming from a dual core, you will LOVE it!! Overclock it!!

What are you running for a cooler? The stock AMD PII coolers are actually really efficient on the PII chips. They've gone up to 4g with them.
oh and NEW out this month and next:
NEW 4** series Femi NVidia cards
NEW AMD 1055 X6 chips 0_o
NEW 890NB MoBo's
It's gonna be a busy year. TRYING not to get sucked into the computers again!