right now the big shots on the block are the Thermalright 120 and Tuniq
http://www.thermalright.com/a_page/m...t_ultra120.htm
(be warned; check your case dimenions, this baby is huge) & probally the king
also, seeing as you are going for a whole system upgrade, I suggest you look at the coolermaster
full tower case that runs about $150.00 at newegg
I have been selling that lately as my favorite child build, they are very roomy, excellent air flow plenty of case fan configs to maximize air flow, I can not think of one thing they need to improve with this case!
you may want to sell of your old system on ebay to cushion the $$$$ shock ?
tuniq:
http://www.tuniq.com.tw/Cooler%20Info/Tower-120.htm
both of these cpu coolers are awesome and will allow you to overclock plenty down the road if you change your mind. The coolers will allow you to overclock your chip by 70% of its headroom capability(which is only 10% of the cpu speed BTW).
The last drop of CPU head room speed needs watercooling to squeeze the lemon. but its a pricey adventure ?
Once you get above the AMD 4400 your overcloking limits are at about 10% anyway, these chips are already overclocked, the only real margin you can extract is by using the 10% slack AMD gives their selling speed
enjoy