Definetly lower it.. looks much better. I only have 17's, but there is still a huge fender gap. Im lowering my car shortly, (I had expected to be doing it this weekend, but the parts arent in. I got my springs and shocks, both apex, from JRP in Mississauga for $995 + tax. This was the cheapest I could find.
Motronix offers the H&R cup kit for close to $1500 + tax or so. Thats for the H&R springs and bilstein shocks.
Coilovers will cost you a fair bit. Im thinking around $2500 or so. You dont really need coilovers unless you want to go real low. The apex kit that I bought should lower me about 1.7" F&R.
Hope this helps.
By the way, Motronix is very helpful and will answer any silly questions you may have.