Problem I'm having with my wired Billion 7800 is it's fine for small downloads like 10mb 15mb it maxes out the line which is fine on speedtests. Get into 100-200mb downloads and it starts stalling as if under a lot of load there is a problem which can effect download speed.
Trying the latest firmware and so far so good. Billion are sending me some new firmware to see if we can solve the throughput issue. It's the wired version so no wireless to turn off. SNTP is supported from the Web interface but last time I used PRTG it was fairly crippled on the free version.