@donbuelke If you shutoff the WiFi on the DSL router and connect the ASUS router (transparent bridge or not) you should get the same bandwidth that you were getting when you were using the ASUS router alone.
The ASUS router basically becomes an access point (it may even have an access point mode).
Are you talking about the wi-fi built into your DSL modem/router/gateway? Yeah, some of those are pretty bad.
My solution, in the same situation, was to connect my router in AP mode. My DSL modem works fine as a router, but the wi-fi function was bad, so I turned off the onboard wi-fi and just substituted my own.