ADSL2+ may add a tiny bit onto the downstream, however it should be noted that ADSL2+ speeds drop like a brick once you get a certain distance away, and by the time you can't receive a full 8Mbps on ADSL1 the speeds you'll see on ADSL2+ are practically identical.
Will find the graphs I had.
This is due to ADSL2+ operating at a higher power and to higher frequencies, however as the frequency goes up the attenuation goes up massively, so once you're a certain distance away the extra frequencies and the bandwidth that you could use them for are too attenuated to be usable so you're back pretty much at square one.
If the 3KM refers to distance from the exchange they are being a little optimistic
The guideline for full 8Mbps currently is 2KM.