Really Slow downloads router crashes

i have always used azereus and it is fine. i download large files in the GB. okay i can get up to like 300 connections per torrent but they go so slow. under 20 kb per second. i have a 6 mb down and 1 mb up. that is a blazing connection aka 600 kb/s per second down and 100 kb/s per second up. i seed at 75 kb/s and i only usually get up to 20 kb/s. why is this. to many connections. also my linksys WRT54G router always crahses after half and hour. if i want to use internet i need to restart the router. my computer isnt the best only a pentium 4 1.7 ghz with 256 mb of ram. so what is the porblem people just have slow connections or do i have to crappy a computer and am using way to many connections. how mnay connections should i have. why are my speeds so slow.