I've recently moved and upgraded to VDSL. Initially I setup the same as my previous setup (which was a Draytek DV120 Bridged to the Asus RT-AC66U) but replaced the ADSL router with a Spark HG630b in bridge mode. When I ran speed tests I would only get 3-5 Mb down and next to nothing up.
When I use the HG630b as the router and DHCP server I get ~30Mb down.
I've followed the instructions on the Spark site on how to run the HG630b in bridge mode and it does connect however I feel like I must be missing something.