some of the allegedly better routers on long lines use the TI AR7 chipset, though there is some speculation that this may be a happy coincidence of TI DSLAM and TI modem.
My personal opinion is that there may be optimum combinations of DSLAM, line and router and as you can only change one of these you should expect to try several different routers.
I recently got a >63 dB line stable that had a Linksys WAG54GS on it (TI AR7) by changing a filter and using a twisted pair modem lead instead of the flat one with a ferrite in it. On another >63 dB line where Wanadoo's Livebox had "never worked" a BT Voyager 205 took up the challenge and synced at 2M with a ring wire removal. A Zyxel AR7 based router on a 57 dB line was highly unstable but a Speedtouch 576 worked smoothly. The same Zyxel worked fine where a BT HomeHub had "never worked".
So I would consider the following four groups and try one from each :-
Globespan virata - Voyager 205, Belkin 7632
TI AR7 - Netgear DG834v2, Linksys WAG54G, 2-wire, Zyxel
Broadcom - Speedtouch 5x6, Belkin 7633 etc - tweakable with DMT tool
Draytek - have longer range firmware and downstream speed limit
Manufacturers have a habit of changing the guts and keeping the model number the same, so later Belkin 7632's may be different chipsets. Corrections and updates welcome.