Whatever you do, do it right. Going with coilovers and aftermarket struts isn't bad, but like these guys said it will cost in the long run because they don't last forever.

I've got GC's and Tokiko HP's in the front, stock struts in the back. The only thing I hate about the Tokikos is that it took a day for the height to settle after I made an adjustment, throwing off the height amost a whole inch.

Either way with a small or large budget, you should get an upper strut bar once your suspension is altered, Nuespeed is recommended because it's a one piece design.

And please get the camber kit and install it with whatever setup you choose. Your tires won't last more than 15k depending on how off your camber is.

It wouldn't hurt to get a complete bushing kit before you start because you can replace some of the old rubbers while you do your suspension drop.

18's look good on a Civ, but it takes more ponies to turn 'em.
I got 17x8's, and they look spankin' but...
'tis drastically slower off the line when I had 15's.

With whatever rim size you decide on, try to get a tire with a Z rating, granted they won't have a warranty, but there's always that road hazard protection plan.

I roll Toyo Proxes F4's, 205 40 17, but they're a grip.
I've had Dunlop Sport SP5000's on my 15's, and they were great at only around a Ben per tire.

Me personally, on a G6 coupe, go with 16's.

Or Tub the fenders and go with dubs, but then it won't move out of it's own way unless you're forcing air or spraying.