I used to use Azureus, then dropped it, as I was a bit ticked off at them, and they were
a resource hog... Any
BT client can max out your router CPU, It does mine... One of the things I've noticed that helps 500% (I can download @ max speed, upload @ max speed, and surf with only a barely noticeable delay) is cFosSpeed.. unfortunately, it's not free, but you can try it for 30 days. OK, and BTW, your global max upload speed in a BT client should be 80 - 90% of your real max upload speed, which you can find by:
Stopping all internet activity (not pausing the torrents, stopping them or closing the client, stop all streaming music, etc)...
Open up www.speedtest.net
, let it find your max upload speed.
-divide the result (which is Kbits/sec) by 8
-multiply that result (now it is KBytes/sec) by 0.8 or 0.9
-Set that result to be your max upload speed, in KBytes/sec
This will optimize things for you... and, if you use uTorrent, use the Speed Guide (CTRL+G in main screen) as well, just make sure your upload is set appropriately after its done.
Oh, and if you find your internet slacking, even after throttling down / stopping your BT, try unplugging your router for 30 seconds or a minute... I have to do that with mine, it's a Motorola WR850G...