With a Billion 7800N router, you can tweak the SNR to get an even higher sync speed.
I was on up to 3.3MB with Zen Internet on ADSL Max but am now on up to 5.5MB with Vivaciti on LLU (ADSL2+).
My stats are currently:
SNR Margin(Upstream) 6.5
SNR Margin(Downstream) 0.6
Line Attenuation(Upstream) 25.2
Line Attenuation(Downstream) 48.0
GPRS > 3G > Wanadoo 1MB 2GB/month > Zen Internet 3MB 50GB/month > Vivaciti 5MB 100GB/month