Cooling

I'm thinking of doing a custom build:
i5 760 (2.8 GHz quad) with coolermaster hyper212+ cooler
ATI graphics card (no idea what yet)
Reasonable 4GB kingston RAM
gigabyte p55-usb3
2 500GB sata HDDs, might add in SSD (3.5") later

I am wondering what kind of case I would need (I plan to Overclock)
It comes down to (I need a gamers case to OC, not to game):
Antec 200 ($61)
This one is cheap, but only has a top 140mm and rear 120mm
Antec 600 ($104)
This one has a 200mm on the top and a 120 on the back
Antec 902 ($121)
This is the same as before, except it also has 2 front 120mm adjustable speed HDD fans.

I was wondering:
a) how much would the front HDD fans affect the CPU temperature?
b) how much would a bigger top fan affect the CPU temperature?
And obviously, what would you buy in my position and why

Also, what are "tricool" and "twocool" fans?

Turns out OCZ vertex II SSDs (3.5") come in a minimum of 90GB so it'd be a 2.5" if that makes a difference