I got a SR MOTORSPORTS Aluminum Radiator. This was well worth the money. On hot day's I used to drive around worried about overheating, but now the car always run cool. The radiator is well designed and over 100% thicker than the stock one. It is made out of all aluminum and is very light. I did not get the chance to weigh it before I installed it, but I am sure I saved a few lbs. out of my RX7. The Tig welds on the Radiator ensures no leaks and is nicely done. It was very easy to install and I got it the next day via UPS.
Check out my how to on installing this radiator. I have a lot of detailed pictures in installing it. I also checked out the Mazda Competition, Fluidyne, Koyo and M2's but found that this was the best bang for the dollar. Let me know what you think of your radiator and I will post it up on my performance parts rater.