ADSL Output power - how selected?

I am using BT broadband plus - the 'up to 8Mbit' service but my line is said
to be 8.6Km long, so I can only expect the service to synch at 576 ~
608Kbit/s, even with best habits over filters and internal wiring. the 'Up
to 2Mbit' service just did not work at all. My router ADSL stats are
below - all pretty typical except the SN margin which was 6dB until today.
I expect we'll be a 576K soon. Those error rates are pretty typical too,
unless it chooses to be wildly optimistic and synch at highr speeds.

My question is related to output power. Is this the power at the exchange?
I see many reported power levels up at 19 or 20 dBm. How is it chosen?
Automatically? Would my service improve if power levels were to be raised?

The HH seems to perform better (at synchronisation, if not reliability!)
than a Netgear 834GT and very much better than the old Voyager 210. Is
there a router model out there which is a really good performer with very
long lines?

Regards
Phil



Uptime: 4 days, 2:50:14

Modulation: G.992.1 annex A

Bandwidth (Up/Down) [kbps/kbps]: 352 / 608

Data Transferred (Sent/Received) [MB/MB]: 25.29 / 133.22

Output Power (Up/Down) [dBm]: 11.5 / 14.0

Line Attenuation (Up/Down) [dB]: 31.5 / 63.5

SN Margin (Up/Down) [dB]: 6.0 / 3.5

Vendor ID (Local/Remote): TMMB / P

Loss of Framing (Local/Remote): 0 / 0

Loss of Signal (Local/Remote): 0 / 0

Loss of Power (Local/Remote): 0 / 0

Loss of Link (Remote): 0

Error Seconds (Local/Remote): 2 / 0

FEC Errors (Up/Down): 0 / 817,138

CRC Errors (Up/Down): 0 / 514

HEC Errors (Up/Down): 0 / 328