A couple of factors as far as the ADSL connection speed goes
* Having the same chipset as the DSLAM may help to eek better speeds out.
* The Broadcom BCM6348/6338 seem especially good on poor lines
On my long > 60dB line I've found the Thomson 780Wl & 585v7 to be very good compared to an AR7 based modem. They are also very configurable. However the wireless is pretty poor.
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