$250? I can see no reason why you should go over $50. Get 8 gigs of DDR3 1600 memory, 2 X 4GB. 1600 speed will be good for if you upgrade to an FX CPU. I like Mushkin because I prefer to buy American, but there are other decent brands too. Check your motherboard approved list before buying.
I'd look into the Thermaltake Frio or Xigmatek Aegir, as shown here:http://www.frostytech.com/top5heatsinks.cfm
Although I think the Aegir is a bit pricey.