DSL Speed Influenced by Modem?

I’m curious if DSL bandwidth is dependant on the modem model.
Everyone knows that a big part in DSL bandwidth is played by the technology used (SDSL, ADSL, VDSL,..) as well as the distance from the CO. My question is, does the quality of the equipment increase or decrease the connection speed?

Maybe someone did or knows of a source of DSL Modem tests/benchmarks…

I’m looking forward to your input.