Interesting you should ask this.
My speedtest from several days ago was 8.7Mbps, more like this speedtest here:
http://www.speedtest.net/result/4971644960.png
CZ says current sync rate: 10240kbps
Now it is 6.6Mbps, and sync speed in router says 7899Kbps
http://www.speedtest.net/result/5029918918.png
http://www.speedtest.net/result/5030934229.png
Test my ADSL line under CZ fails...
What gives?!
Your line could be stabilised here, the speedtests aren't too bad for the line sync.
PM me your number and I can try and have a look at what's happening here.