You don't *NEED* AS5, but it's supposed to be best on the market right now. People claim like 2-3 drops in temps...but it needs like 200 hours of your computer being on for it to get to its final 'stablized' state...so basically you can't just apply it..turn on your computer and hope for a cooler temp...gotta wait atleast a week...Id suggest buying a small tube of it if all you have is generic. That fan is a nice fan, I have both the Aero 7 and the updated 'Jet 7' personally the heatsink on the aero 7 is better and the fan blows air better on the aero7....I think they went too far out of their way to make the other look like a jet and sacrificed air movement...that aero 7 has some nice wind coming out of it...
What are your current temps?
I would say if you got stock heatsink right now....then you should see atleast a 10degree drop using AS5 and that heatsink you linked to. Remember to thoroughly clean off your cpu core with some 99% isopropynol alcohol or something of that sort....needs to be nice and clean...don't want goops getting mixed up on ya