I've lurked these forums for a while but only recently joined up. I'm just wondering if someone could answer some questions I have about my house wiring and my attenuation, which from reading around here and sbiddle's blog seems to be rather high (and yes I have read the stickied post here)

I'm with Telecom at the moment, on one of their 150GB home packages. I live in Epsom so I would have thought that cabinets would be rather frequent and I shouldn't be getting attenuation this high. Looking on http://gis.geek.nz/infrastructure.html#chorus_cabinets seems to suggest that I have a few cabinets around a couple hundred metres away, though I'm not sure how accurate that map is. The attenuation seems to suggest a distance of ~2.5km.
I know the first suggestion people have when someone complains about their speed is that it is the wiring in the house that is to blame. My house is rather new (~7 years) and I believe is wired in accordance with the guidelines in this picture I found(edit I can't embed links apparently but it was the TCF guidelines picture). Most rooms in the house have 2-4 8P8C (I think that's what they're called) jacks for either ethernet or phone connections. Each jack is numbered and connected to a central box in the garage: https://i.imgur.com/VggjEXI.jpg.
On the right is the tv cables that go through the house and on the left is the cat5 system. All the grey cables are connected to a "primary telephone module" https://i.imgur.com/ExgF5dt.jpg I believe this splits the telephone line and allows us to plug in a phone into one of the 8P8C jacks. The black box on the left is presumably a master filter (it looks like the pictures I've seen around here). The blue cable coming out of the telephone module I believe is for our monitored alarm. The place that has the two grey wires right next to each other has the adsl line on the left.
Because we have a master filter and the wiring is set up correctly (at least I think so), I'm not sure what the reason for the slow speeds/high attenuation is. One thing I had thought was that it is to do with our modem/router setup. The ADSL line mentioned in the previous paragraph is connected to one of the 8P8C jacks in this box and then the modem/router is at the other end in the office. One of the plugs from the back of modem/router is then plugged back into the wall, where it comes back down to the box and gets split by the white thing in the bottom of the box from where it is sent back out to the rest of the house.
When we moved into the house I believe there was a modem inside this box but it stopped working so we switched to our current setup. Would the distance that the ADSL line has to travel through the house before it reaches the modem/router affect the attenuation? I would have tried to plug the modem/router into the box to test this theory but I wasn't sure how - the ADSL plug from the phone module is an 8P8C plug, while the modem/router takes a normal ADSL plug which is smaller (we have a cable that is 8P8C on one end and the smaller ADSL on the other end to connect the modem/router to the jack in the wall)
My other thought was that the master filter isn't connected correctly as the wires from the top of it go into the phone module but nothing is connected to that point. I don't know much about how they work though and I didn't want to mess around with the phone line so I didn't play with that.
Sorry for the long post but I hope someone here is able to give me some guidance on this :)
As a side note, I'm also thinking of switching to either Snap or Orcon because their plans allow for more data at similar prices. I'm concerned about their service however, both in terms of customer service and actual internet connection. Is there anything to worry about? Telecom so far has been perfectly fine but the 150GB limit does stretch us.