The 2600+ will be fine for gaming, They dont run to hot with a standard heatsink if you use it at default speed. If you wanna O/c the cpu then you should buy an after-market fan, doesnt take anythig special to keep it cool round 3200+ speeds from my experience (built around 6 Amd machines for freinds and family) you are also missing ram there less you are switching it over? i would reccomend pc3200(400mhz) if you plan to over-clock the system i prefer corsair but there are several decent brands, two sticks at the same rating will also give you an improvment over a single stick
LJ