Wilsons Sandbox

Hello all, I recently bought my first KiLleR. It's an A4. So far so good! I love it! It's just what I expected! (It should be, I've been reading/lurking on this and other boards for more than a year!) One thing I'm not crazy about is the gearing for my anticipated riding adventures. I have not done much (although some) offroad stuff but I have already determined that too much clutch work is involved for my liking with 15 teeth up front. I bought a 14 tooth and now I want to replace the chain and rear sprocket at the same time as I've seen recommended. I was just going to get a basic steel 43 tooth rear likely from sprocket specialists. But I wasn't sure about the chain, and how I figure out A. what size, B. what type, and C. what quality level (and how I can tell the difference especially with B and C). Any help you can give would be teriffic! Thanks, and as always, ride safe. Tom