What can this connection handle: a dedicated SDSL line with 6000kbps / 786 kbps, all it will be hosting is a site and a forum, how many people do you think it can handle at once constantly browsing the forums and site, also would i be better off getting a cable line with 2 mbps down / 786 up?

No redundancy?

Problem is you would need Up more than Down, so if your provider could get you 786K down, and 2000+ Kbps up, then it should be cool.