bikermomma, this web site helped me learn a lot about gearing. I think it has the information about chainrings/cogs that you are looking for.
http://home.i1.net/~dwolfe/gerz/howto1.html

I'm in my second year of road riding and as a recreational cyclist I can say that I doubt you (or most recreational riders) can tell the difference between Ultegra and DuraAce components. So I would suggest that you get the best you can afford but don't worry if you can't get the top of the line in whichever brand you choose. Test ride them and I think you'll see this is the case. I'll give a +1 on what everyone else has said about fit. Good luck in your search. I hope you find the perfect bike for YOU.