My suggestions:
Motherboard: Rampage formula for "safe and stable" is a little overkill generally the ROG boards are built for extreme overclocking my suggestion for the motherboard would be
Asus P5Q Deluxe 775 P45 DDR2 | FORCOM webshop
CPU: Quads are cool but most games and apps don't utilize all 4 cores completely my suggestion
Intel Core2 Duo E8600 3.33GHz 6MB Boxed | FORCOM webshop or
Intel Core2 Duo E8500 3.16GHz 6MB Boxed | FORCOM webshop these cpus will easily clock 4ghz safely
CPU Cooling:
Ultimate CPU Cooling Solutions! USA and a good fan say
Noctua.at - sound-optimised premium components "Designed in Austria"! or
OCZ Technology | Products | Cooling Products | OCZ Vendetta 2 CPU Cooler
Memory: 8GB personally is overkill
Ascent XP2-8500 DDR2 - Mushkin Enhanced Can't go wrong not sure of availability since you don't seem to be from Canada
VideoCard: Thats about right Asus has a better warranty than most.
Harddrives: This is pretty interesting Raid 5 would be pretty quick its also has redundancy although its very expensive, however personally I would go with a 1 large drive for my OS say 1TB and 2 velociraptors in raid for games.
Powersupply: Excellent choice can't go wrong with Corsair, as far as quadfire is concerned you'll need 1200w or greater to be on the safe side.
Case: Cosmos would be my choice over the Antec 1200 although you should check out Lian Li and SilverStone and always leave a little extra $$ for case fans.
Monitor: Didn't see one if you're driving this computer with a 4870x2 hopefully you have a 24"-30" display already you shouldn't be gaming at anything less than 1920x1200.
OS: Thats fine hopefully its nice to you during the installation and doesn't cause to many headaches.
These are just suggestion and the intent is too offer some savings personally this is probably the setup I would be running if I were to upgrade from previous setup and again welcome to forums hope you stick around.
P.S. From Belgium I take it