The E6600 is not even available at newegg any more. Can you still find it in Peru? If you can, make sure it doesn't cost more than the Q6600. I remember the last time I checked prices the E6600 was a lot more expensive than an E6750, even though the E6750 is better.
In a single-threaded application, if no other applications or background processes are running, the E6600 and Q6600 are identical. If you have 3 or more single-threaded things running in parallel, or a multi-threaded app, the Q6600 wins.