I got a similar set and they have been good to me. Had them about two years now, holding up well and they are noticeably lighter than standard 32H training wheels. I raced on them in the rain earlier in the year and that worked out fine. Better braking then my Zipps in the rain...

I don't think that upgrading small parts on that kind of bike is worth the money, if you're going to do it, just get the nicest wheels you can. Pedals and saddle you did right by, other than that get a different bar if you don't like what you have. If you want a lighter set up eat smaller meals and ride more. Lighter bar/stem you won't notice. Lighter brakes you won't notice. Faster and/or lighter wheels you will notice. Save your money for a rainy day or a boutique frame.