The noise margin is much better. Have to ask: Do you have one of these installed?
Micro filter.
You should have one for each POTS ("Plain Old Telephone Service") device. Only the modem should not be filtered.
With your noise margin at 14 dB, you should definitely be capable of faster service. Technically, you would lose some margin as your speed goes up; but if your line can hold 10 dB at 6 Mb, that would be your expected maximum speed.
P.S.: PVC = 8/5, along with ADSL2+, tells me you are in legacy Bellsouth territory. The details of your expected max speed are a bit different from what I know in legacy SBC territory.