Here's the deal. Over the next few months I want to add to my car: An Rs4 style body kit, some Eibach Prokit front and rear coil springs (lowers about 1 or 2 inches), and some b5 Celebration wheels (Tire Size: 235-40-18, Wheel Size: 18X8, Bolt Pattern: 5X112, Wheel Offset: ET43).

My questions are: Will I need new struts to go with the new coil springs? Will my car bottom out on speed bumps, RR crossings, etc? Will changing the wheels or coil springs un-calibrate a recent alignment? And lastly, are all these parts compatible with one another?

Any enlightenment will be greatly appreciated!

You will need aftermarket struts or you'll wear out yours pretty quickly. Changing ride height will likely nullify your recent alignment so you'll want to do it again (Firestone offers lifetime alignments for $120 - well worth it if you're keeping the car awhile). I doubt Eibach will drop the car low enough to bottom out much, but that all depends on the speed you hit them at, and how high they are. The parts are compatible, but I'd suggest 225s rather than 235s - a 225-40-18 will keep your speedomoeter and odometer calibrations essentially unchanged.

^^ I agree. You might not need them right away, but sport struts will not only last longer and handle better, they might drop you another inch or so.

Also, didn't know about the Firestone alignment thing, I wish I'd have known about that when i bought my car..(i've had two in 6 months, one at the dealer when they replaced my front upper CA's, and one when i hit a huge pothole and bubbled a tire). That would have paid for itself already lol.