Just oto clear something up: it would seem that stupididiot is suggesting that the more bandwidth you give to uploads, the less you'll have left for downloads. That is untrue: unless I've read the post wrong, then you must know that upload and download bandwidths use different "slots". That is why when advertising connections, ISPs put two different bandwidths (of course, most everyone looks at the big number only...).
Soooo, in order to set your upload bandwidth, you have to also know how much it is.
Did you read
this ? I'm pretty sure it will help.