reply to Herb11 All Tiers below Turbo will be provisioned to a D2 modem whenever possible. This is a bit of a double-edged sword in that you can achieve nearly 'Extreme' speeds when Powerboost is available, but as previously stated the single D2 channel may also become congested during peak usage hours. If you want a D3 modem which will almost certainly provide you the 15Mbps but no more, have Turbo or higher installed and pay the pro-rated difference in cost. It will future-proof your network for possible upgrades and in the end the 4+ bonded-D3 channels will be more consistent connectivity than any single D2 ever could.
TL;DR: have Extreme installed and pay the difference to get the equipment, then downgrade via phone back to Standard. -- I see what you're saying, even though I'm really just listening...
reply to Herb11 From what I've seen from people with Standard Internet they seem to give out Docsis 2 modems. Personally which I think is a horrible idea, because otherwise they are way more likely to see slow speeds at peak times because the D2 modem can only use one channel and if the one channel gets congestion your speeds dip. I do believe that Turbo 20Mbps and up they give you a D3 modem.