Nissan: vibration woes !!

I recently purchased a Maxima SE 2003 with 15k miles and immediately noticed
a vibration around 60-65 mph with the original Bridgestone Potenzas. I've
heard these tires are piece of junk so I asked the dealer to install new
tires. They installed (and balanced) a new set of Cooper Lifeliner SLE
225/50/17. Since then the vibration continues. The alignment is ok and got
tired of balancing these tires at numerous places. I noticed 2 of the rims
are bent but not much. Is a minor bump on the rim enough to cause such
vibration or are these cooper simply cheap stuff? I've heard that the Kumho
ECSTA KH11 are good for this vehicle and won't kill your budget. Anyone with
experience with either the Coopers or the Kumhos?

You can check the runout (or out-of-roundness) on your tire/wheels by
jacking up the car and giving them a spin. If they're out more than a
couple milimeters, you probably have either a bent rim, out-of-round tire or
both. Wheels that are slightly out of round can be compensated by
balancing, but if it's more than normal tolerance, yer gonna need some new
rims.

Chris
90 & 94 GXE's