Ignore your attenuation figure in the modem, it means nothing. The 10.8 figure is done at a different frequency and will differ to what your modem says.
A rule of thumb, if you are on Chorus gear and get 16Mbps or higher on ADSL2+, then good probability you can get VDSL. 14-15Mbps, you are at the lower end and may or may not get VDSL. Less than 14Mbps and you are unlikely to get VDSL unless you currently don't have a master filter and your home wiring is very bad, which means the VDSL install will fix this :)