I've had a number of friends pick up ropes at justropes.com

As hikermor said REI is also very good if you wait for a sale.
I also buy a lot of climbing gear at Eastern Mountain Sports when the run sales.
Both REI & EMS will match each others prices.

Standard disclaimer.

I'm treating my response as you know what you're doing and what you're looking for. For anyone reading who does not climb..nobody should be buying ropes and trying this without proper training unless you're idea of fun is to be broken or dead.