Awesome! Really informative. You know I had a play around with some of the settings on my router this weekend (however it seems that there was actually very little I could do - I'd like to think it's because I'm just stupid but I fear there really is nothing much really in my power) and I found that I understand (or at least understood before coming across this post) very little about the actual implementation details let alone the various settings that I could play with to make me think I could improve things.

Yes Attenuation/SNR is the most important, it can still be improved by building a dslam/exchange near your house or your line can get moved to a closer dslam/exchange.
Tell me how!!! I would kill (well probably just dismember) to get a 10 Mbit/s connection going here but apparently my exchange only supports 6 and even though I asked them to "up" me I still sync at less than 4...funny how we clutch at pipe dreams?