Asus 4870 512MB Black Knight vs nVIDIA GTS450?

Hello! I am currently looking to upgrade me GPU, and I work at best buy and get a HUGE discount on Graphics cards, and the GTS450 is the best one we have in store right now and was wandering if it was worth it to buy this? upgrading from a Asus 4870 DK edition.. and also, is the GTS450 better then the ATI5770? Thank you!|||Ati 5770 still rocks. But for the budget you can choose the gts 450. The 5770 has eye finity and many other features which are still comparitively less in gts450. You could still choose NVidia for the price point.