I wouldn't bother with an aftermarket exhaust. There isn't much, if anything, to be gained in performance or weight over the stock pipe. (There is some performance to be gained, but not without also running a fuel control box to tune the engine to a new pipe. It's all too expensive and too much of a hassle to me)
The silencer is a different story, you can loose a good amount of weight from that. A silencer is actually the best bang for the buck in terms of weight loss for a PRO.