Any one of those will be great cards for gaming its up to you to figure out how much you want to spend. Also you should list your system specs for us so we can suggest the best card for your system.
The HD5830 and 9800GTX+ really are not good buys at all. The HD5850 and HD5770 are although the HD5770 is $20 more than you need to spend. http://www.newegg.com/Product/Product.aspx?Item=N82E16814161317
We need to have more info about your system to make a real recommendation(CPU, PSU, resolution.)
heres my specs:
i7 920]
rosewill 750w
p6t deluxe v2
western digital 15000 velociraptor
current VGA is his radeon 4870 ice-q turbo but it freezes some times and makes combat arms' charcter/people/zombie lag like hell. and it was not cheap...180$
tuning up the memory clock to 1015mhz in catalyst. i got the latest version
btw do u play combat arms? it works fine in all my other games exept combat arms.