>some thoughts<
I`d drop azureus and try a different torrent app.
Even with a 10+ Mb connection i`d still see slowdowns elsewhere with browsing etc no matter how well configured i had the frog,the fact that it uses java dont help matters much.
I`m assuming your using Ubuntu so i`d really recommend trying ktorrent or deluge.
I used azureus myself for quite some time till i tried ktorrent and it does a much better job all round i`ve found(as have many others)....better speeds,less resources and no slowdowns if i`m browsing the web at the same time(which is rare anyway)
Azureus is good if you like bloatware
EDIT:Ktorrent = Kde not being a problem in a gnome environment of course