Well, you're in luck. Those three parts I listed in my first post (CPU, motherboard and RAM) plus your 650W Antec EarthWatts PSU (a good PSU, for what you want IMO) comes out to be $399.96, or $449.96 with 8GB before shipping.
However, if you're not adverse to using Micro-ATX (There's really no reason to be, they're just as powerful, just smaller), then you can go with an
ASRock H67M LGA 1155 Motherboard.
The H67 series aren't made for overclocking a CPU, so you'll be good on that since you don't really want to anyway. It will offer the performance you need on a good level while offering USB 3.0 and SATA 3 (6Gb/s), however it does not have the new UEFI BIOS (at least it doesn't list it on the Newegg page).
Add on a
Corsair TX650 v2 PSU, which is vastly superior to the Antec EarthWatts series, the total comes out to $409.66 before shipping.
If you want to shave off $10 for the benefit of the UEFI BIOS (It really is a million times better than the regular BIOS), then go with the
ASUS P8H67-M LX LGA 1155 Motherboard.
All this is with
8GB of RAM, btw.
I would still throw in a decent GPU if you plan on playing a little DA:O and/or DA II on the sides
But that's just me.