The -1 on the front is usually the easiest to do, and offers the most difference. It's simple math, ratios. Might want too try that first on your trashed chain, just to see if that's what you want. That way, if you decide you want more, you can get a +2 for the rear, and right chain. If your chain is as rough as you make it sound, I wouldn't run it much longer than just enough to tell if the -1 front is enough. Changing both sprockets and the chain all at once is the best. However, it's likely that the front sprocket is trashed, and the rear still in very usable condition, making it less necessary to change the rear. Steel vs. aluminum...... Full aluminum sprockets have there place, and it not on a bike that's rode hard on the street. On the track, things are much different, and one would expect to replace parts more often, so why not go with something lighter..... I do like those sweet looking aluminum hub, steel outer, sprockets! They even look "blingy" if that's what matters to you.