I opened a thread not so long ago on this subject.
http://www.cliosport.net/forum/showthread.php?t=281445
I opted not to go for a 4-pot conversion. Pedal bite usually isn't as sharp as when using standard calipers due to the increase in pressure needed to operate the extra pistons in the calipers. A master cylinder with greater pressure matched to the new 4-pot calipers will probably sort it out.
Some are very happy with set up, prefering a more progressive (soft) feeling rather than that intial sharp feeling with the brakes. But once firmly applied braking is very good and better than standard
Although one is usually very happy with a simple upgrade costing far less. PF 97 pads combined with Brembo Max discs really WILL give an increase in this area. :star:
Just make sure you clean the wheels every two to three days. Brake dust is horrendous, and will actually damage the alloy if left on to build up!