Just about all you can do with the client is adjust the nice level.
So you would run it...
./setiathome -nice nn -proxy xxxxxxxx
where nn is a number from 01 to 19
The higher the number the lower the priority, default is 10.
Be careful running it between nice 01 and nice 09 though, you don't want to upset anyone.
If you have ownership of the machine you could look at tuning it eg shutting down unwanted processes etc..
cheers,
Col.