Core Parking is a feature that puts unused cores into a idle state.
For some people it can cause stuttering in games as cores park and activate.
It is possible to show parking in Windows power options As i have done with my system.
http://www.tomshardware.com/forum/id-2177396/thread-schedular-6350.html
For a good budget cooler i would recommend a Cooler Master Hyper 212 EVO with a extra 75cfm fan.
A lot of people would tell you to get Artic Silver 5 thermal compound but testing does show that it is little better than the stuff that comes with coolers. I do use AS5 myself.
It is hard to say exactly the clock rate you would be able to achieve as every cpu is different and is called the silicone lottery by many.