If you want to keep right on your $150 max budget then I think the HD 7770
would be a good card.http://www.newegg.com/Product/Product.aspx?Item=N82E16814102993
This one is currently on Newegg for $149.99 w/ FREE shipping and a $15 rebate which will eventually bring the price down to $134.99.
The Vanilla HD 7770 trades blows with the HD 6850. HOWEVER
this one is the GHz Edition
which should make it faster than the HD 6850 in the majority of situations. Closer to HD 6870 speed with out the HD 6870 price.
Plus it has the Vapor-X cooling built in to the heatsink.