The post is full of wrong info.
First of all only 125 GTS has been produced not 250. And the weight difference between M3 and GTS is around 150 lbs not 300.
Also 240 lbs lighter CSL has no A/C, no radio, no Xenon which were chosen by most of the CSL owners.
They are great cars, no doubts. However, CSL is one fine machine which looks perfectly tuned from Factory but GTS on the other hand just looks plain aftermarket..