New to watercooling, and i need some help

Hey guys.
I am new to this watercooling thing and i wanted to make a custom loop with red tubing and destilled water, a resevoir witha pump attatched to it, and i want to cool my GPU and CPU with a 2*120mm radiator. I was wondering what type of fittings are the best? the push on, high flows, or the push in with a clam around it or straps.
and how cool will the CPU and GPU get? i have a HAVIK 140 atm, and it's at 25C and 28C when gaming heavy load.


My PC specs:
CPU: AMD X6 Phenom II 1100T Black edition 3.6. (replacing with a FX 8350)
GPU: Asus GTX 670 DCU II
PSU: Silver Power 500W (i might replace this if it is'nt enough)
RAM: 4x 4gb 1600MHz Corsair Vengeance.
MB: Gigabyte GA-870A-UD3, Socket-AM3+
SSD: Corsair Force 128gb
HDD 1x 300gb Western digital 1x 500gb western digital
Case HAF 912 (is this case big anough, and do i need to do some modding? i have added a 200mm exhaust fan on the top for extra cooling)
And where would you recommend that i put my resevoir?

Also i wonder if my case the HAD 912 will in any way hold a 2x 120mm radiator, it doesn't seem to fit anywhere, and will a single 120mm radiator be enough to cool both GPU and CPU ?

Thank you in advance