I run Hx wheels in the summer and VX wheels with snow tires in the winter...The HX's at right under 12lb each...if you want 15' I've heard the GSR blades are fairly light...you might want to look aftermarket because most 15' Honda wheels are fairly pricey...
I just skimmed but for aero mods on the Del so I have a grill block, a front lip, the car is lowered, I am making a piece for under the rear to keep air from being caught in the bumper, I have some VG's I am mountingon the roof and I am fabricating a civic hatch spiler above the rear window to reduce turbulence...
For your CRX I wouldn't worry about a spoiler, the only one that might have a positive is the EDM (I believe its the European SIR Spoiler) that comes straight off the back...but the CRX already has a pretty good cd...
Oh also, Dan was talkign about my VX with the full grill block, the VX also has a much smaller rad then your CRX...its a about 1/2 the width but it is also only a single core unlike most of the 1/2 rads...it was the smaller honda rad I ever saw and the car never overheated...but I only had it in the winter before the car meet its fate