Welcome aboard!
This is pretty hilarious - I too had a 2004 SpecV before I traded for my 08 3.5 coupe. We also have very similar ideas as far as what we want in our coupes.
http://forums.altimas.org/zerothread/320208
This link will take you to a writeup for the Eibach install. If you scroll down a few posts, there's an avatar with a sideshot of a coupe on stock wheels with the drop. Thing about the springs is they require modification to the bump-stop in the struts, which will void warranty on the suspension to my understanding.
I go in for dealer service according to my schedule for anything besides oil changes. I've brought it in for the airbag sensor recall, and I currently have intake and axleback exhaust and have never had any issues with the dealers refusing to work on my car for any reason. There are some good people where I go though... lots of the service guys are gearheads and drive Zs anyway.
If you want a deeper exhaust that's not gonna rattle the fillings out of your teeth and give you a tone closer to the G/Z, look no further than Tanabe, my friend. I just bought mine and it's amazing. Fits perfectly. Took all of 30 minutes to install in my driveway - retains all OEM fitment down to the ground wire and hangers - looks and sounds absolutely wonderful and very tolerable on the highway. I'll reply here again once I finally get videos posted.
Enjoy the car! Post a pic or two!