At some point, there are diminishing returns for the increased horsepower.
I don't think the 335i is too heavy, but the TSX feels notably more tossable and I realized it's as GB noted, it's because the 3'er is so planted. Great 50/50 balance, zip/zero/zilch body roll, biiig tires. You can't upset the car. Which is really impressive and great! - don't get me wrong - but it's true that, unless you track, you won't feel it close to its limits.
That said, I'm really starting to feel the urge to get into light tracking... but I'll start with some performance driving courses or something...