The tool you refer to told me I'm 3600' from the CO. Turns out, after months of frustrations, that it's actually ~8000', depending on how they measure it. So, do not necessarily believe the results you've gotten.
At my distance, sonic has not been able to deliver ADSL2+. I'm getting ADSL1 because that's the only mode that's been remotely stable. What I'm told is that I'm too far and the line quality (line attenuation 38-39dB) is too marginal for the system to deliver even ADSL2, let alone 2+, to me.
I get 3.5/0.6 Mbps with erratic stability. Oddly enough, when I had AT&T's DSL (same lines, same CO, obviously) I was getting 5-6Mpbs down and 0.9-1Mpbs up.
We continue to work on it, but I'm not hopeful I'll ever see ADSL2+. I would, however, like to see a stable line at the speed AT&T was able to deliver.
Just a single data point. YMMV.