Possibly depends on how long the line is to the exchange, could you post the router
I've tried several routers with various chipsets connected to the exchange which has a DSLAM with TSTC chipsets and the "best"
for my connection is a router with a Broadcom chipset ..... I'm using a Netgear DG834GT just now.
The downstream attenuation for my long line is around 60dB depending which router is connected.