A different point of view here....
I currently own an Audi S4 - 340 HP - that I have tracked numerous times.....I am 48 years old, so perhaps that is a factor here, but let me say that at this point I have less interest in raw power than in being able to rev out an engine to get maximum performance out of a car. I have a 128 on order - Msport package. I have driven both cars, and because of the acceleration on My S4 - the 135 did not do that much for me. In some ways the extra power is a bit of a crutch. It made the manual feel a bit "automatic" in that you don't have to downshift to get thrust. After a while - the pure acceleration fun wears off, and what you look for is a car that is as light as possible, with great handling, that still meets whatever needs you have for practicality.
On the track, the drivers I admire the most are those in the lower power cars who can maintain momentum in the corners and challenge the higher HP cars. There is something about being able to run a machine at full throttle that is really exciting. The 128 lets you do that more often that the 135!