4pin molex fans? which fan to buy?

Hello together, I've found a really good special offer, and wanted to ask if I should buy it. Usually I would inform myself but this offers seems not to last for a too long time and I have to do other stuff atm.

The product im talking about is a fan called Nanoxia Highflow FX+12 - 2000 PWM or the 1250 PWM version of the same fan.(http://www.performance-pcs.com/catalog/index.php?main_page=product_info&cPath=36_49&products_id=24880)

They both "use" a 4 pin molex connector and my first question is If many Am3/am2+ motherboard which aren't to expensive (f.e Gigabyte GA-MA790X-UD4) would support having two aditional 4 pin fans (+the fan from the Xigmatec S1283 + 2 fans from Antec 300).
I count 5 fans in total but the descriptions of the motherboard say's 4x Fan (I don't know if 3or 4 pin).

Is the fan of the Cpu included when saying 4x Fan or does it mean you cann install 4 additional fans (which I want)

my second question: which version should I buy one with 380–1.250 turns per minute or 600–2.000 I want to overclock and need good cooling but I don't know how many turns/minute make sense.

Does it make sence buying such fans or should I just buy simple 3 pin fans?

Thank you Erdinger

Ok i've looked at the pc i have right now and reckognized that only the cpu fan has 4 pins (no idea why) and that even with 3 pins I could adjust the speed of the other fan... (Bios it's more silent now ^^)

Can someone please explain the difference between 3 and 4 pin and which I should buy as chassis fans and why?

Kind regards Erdinger

thanks a lot that helps