I also have long researched on the internet, was ultimately at Linksys, because many other companies still have problems with the stability of the modem to marginal 16000 connections.
In the meantime, my Fritz box had to serve as a modem! But several Sync. Daily loss and poor voice quality in simultaneous download strengthened my desire for a new "all in one" device.
About the WAG200G I found very little feedback on the Internet, but the company has always been sympathetic to me - So I ordered the device.
With the Fritz box I had gross 14400/946 Kbits / s and several synchronization losses per day.
The WAG200G runs for a week with stable gross 17205/995 Kbits / s without any interference, despite a SNR (signal-to-noise ratio) of 6-6,5dB.
From 6dB stable operation between the modems is possible.
I think that says it all about the quality of the gateway, in particular the integrated modem.