My brother, who out geeks me like Yoda out jedis a stormtrooper, and has cisco certs and MS certs and a BSc in computers [1], spent AGES working on this problem.
He created a firewall QoS management system that basically kicked ass.
He assigned different priority bands and put various ports and what have you (like I said...him yoda, me grunt) into them. The upshot was that we had p2p stuff in the bottom band so as soon as someone surfed, azureus was throttled near to death, we could also divide the bandwidth into 3 equally between the 2 desktops and the server , or favour any one of them. Each individual machine's "chunk" of the bandwidth (be it favoured, fair or deprived), was then further tuned by the priority bands. Worked brilliantly. It would sit on fair or server-favour most of the time, and I could still surf fairly well, but downloads were poor and azureus was strangled, if I needed the whole pipe, a quick click to favour my machine and I had the whole connection to myself (more or less, obviously other stuff still got in and out, and anything I left slack was up for grabs). It could also prioritize acknowledgement packets which maximized the speed at which azureus could upload before it effected the download speed.
We stopped using it when we got a better connection, but I think he still has the scripts, and am 60% sure he added it to his floppy firewall (wee sh** used to buy junkers for a tenner, compaq P60's that sort of thing, strip out the sound and HD's and anything else surplus to requirements, shove his floppy firewall disc in them, and flog them for £300).
If you have a paperweight PC somewhere and can do a wee tiny bit of Linux, I could see if I can blag an image file of the floppy for you. Sounds like it would be ideal for you.
Then again, repeated use of the LART is probably a better idea as has been suggested above.
Or just leave a spade and two bags of quicklime in full view.
[1] and yes, he IS a useless dipstick and commen sense computing)
