InstallerUFB:
The other thing about dual or quad paired BB/DSL is that the copper pairs have to be balanced as well (two or four identical pairs) - especially for the longer distances from the equipment. Ok for Urban/commercial environments - not very often found in rural ones (because it doesn't normally mater for single circuit use)
Cost wise you will be at least doubling your line rental per month from Chorus (Via your RSP)
Never known the above mattered, that would make a further complication with any multiples i suspect.
Always found Proper bonded dsl to be fairly higher than doubling the line rental, to the point it wasnt worth it at all.