the power stats will be reported by your router somewhere, not all routers may show it but even the router aol provide show the stats.
Rather then looking for it try this.
Move the router to the master socket then recheck the stats to see if the downstream noise margin goes up, if it shoots up you all good and the line is capable and you have found the problem.
Although attenuation is a good guide to the general line distance and quality it isnt the be all and end all and the ultimate deciding factor is the noise margin, your noise margin is poorer then mine, I would probably have over 20db on a 2mbit synch.
I entered your values in the speed estimator on dsl zone website.
The adsl2+ checker only uses attenutation and assumes the noise margin is healthy and rated you at 8-12mbit.
The adsl1 checker also uses the noise margin and gives this for your line stats.
"Based on the values you entered, we estimate that your line can support around 2.3 - 3.0 Mbps"
I wouldnt panic yet tho, the chances are the problem is local and will improve when using the master socket.
http://www.dslzoneuk.net/maxspeed.php