1- The X6 comes out the 26th of April, that's in 3 days.
2- If u want a quad core, buy a quad core, Phenom II X4, i5 or i7. The processor depends of the budget.
3- Since is a new mobo with new processor, u also need new RAM. 4GB 1333 for AMD is a good option. 4GB 1600 for i5 and i7-8xx series or 6GB for i7-9xx series is the best option.
4- For mild OC you can go with a CoolerMaster Hyper 212+, is the best option price/performance for CPU coolers.