Simple Push-Pin Aftermarket Coolers:
Rosewill RCX-ZAIO
Rosewill RCX-Z90
Assuming your Motherboard Tray does not have a hole and your willing to take the motherboard out, then i recommend this CPU Cooler:
CORSAIR Hydro Series H60
Also for Thermal Paste, while AS5 is good, there are some better options that will lower your temp by a few Cs. Here are some examples:
ARCTIC MX-4
GELID Solutions GC-Extreme
G751 Shin-Etsu This is a really good Thermal paste but is thick making it a bit more difficult to apply.
Prolimatech PRO-PK1 Currently out of stock at newegg
PK1 and Gelid seem to be getting some really good reviews, followed by Shin-Etsu then MX-4.