Actually, I should clarify things.
I use a VPN connection from two different Watchguard firewalls (one on FTTC, one on ADSL) to two remote sites. One has ADSL2+ with an upload speed of 1Mbit/s. This is the connection which had the Netgear DG834G. It couldn't achieve anything close to 1Mbit/s over VPN and was incredibly flaky even though the line was rock steady.
The other remote site has FTTC and had a Draytek 2850 from the start. This is the connection that works at 20Mbit/s over the VPN - the speed is limited by the FTTC connection.
I can't get that over the ADSL2+ link of course but switching the Netgear out and putting in a Draytek 2850n, in anticipation of FTTC, has transformed the performance in terms of reliability, throughput and no packet loss.
As you have tried a Draytek at the remote site, it's possible your local endpoint may not be 'man enough' to handle the VPN. If it's another Netgear DG834whatever you're sunk.
Edited by caffn8me (Tue 04-Jun-13 16:20:29)