If you have a coupe, the cheapest and easiest way to get 50% more power in roughly the same car is to sell your coupe and get an M3.
If you are committed to a 4 door E46, then S/C or S54 swap, I guess. LSD would also be a useful item to swap while doing this. I never really knew how big a difference the LSD makes until I went from my ZHP to my M3. Of course I had driven many other LSD cars but when switching platforms there are so many different variables that it's hard to tell what role the diff is playing. Here in the same E46 platform I really notice the difference an LSD makes.
- Luke -
2012 Audi S4 6MT
2009 GMC Yukon Hybrid
2004 M3 Convertible 6MT (sold)
2004 330ci ZHP 6MT (sold)
2002 Audi S6 (sold)