The 430 is a monster, and hard to compare to the 360. Discussed more thoroughly in previous threads; the engine is an evolution of the Maser's 4.2, and should be much less maintenance intensive as the 360 is. (in particular timing chains vs. belts) The exhaust note of the 430 is downright mean, and you'll never forget you're driving a Ferrari.
The Maser is actually a better comparison to your Porsche than the 360, except the Maser has usable backseats (if you need them). Unless we are talking about convertibles.
Nice 360 Modenas can be had for $125-130k, which is really only about 10-20k more than a new Maser GS, but without the warranty. We have a like-new '04 Rosso Corsa 360 Spider with only 2k miles, and great options, priced about $220k (yes, more than it was new), and the 430's go up quite a bit from there.
- Mark