CX is the lightest one but the vx is already wired up for vtec. engine swaps would be easier in the vx just for that reason. A few question for you wAnTtOsTrEeTrAcE. Are you mechanically inclined? Do you have a basic understanding of how a car works? are you willing to get a lil dirty? Are you ready for the experience of a life time and gain a priceless amount of knowledge? If so go with either the aforementioned civics(cx/hx) but don't spend more then $3500.00 (and thats being generous) If your not look at spending at least $4500.00 and up for a 92-95 Si remember what makes the Si heavier then the cx-vx is A/C pwr window, locks,sunroof power steering and sound deading material. Granted a VX or CX may come with this optional stuff besides the sunroof but they are all removable. If you do remove the power steering do it right,don't mean just pulling off the belt, remove everything i.e. pump, rack, lines an reservoir. reason being if you run a power steering system without pressure you will blow the seals in the rack and the pump. Plus you'll have to fight the rack and pump when steering. Pick yourself up a manual rack out of a cx dx makes it easier to steer
Just my 2 cents