We did a lot of these modem replacements a few years ago to enable people to move up to faster speed plans. There haven't been so many lately as pretty much all those old Alcatel chipset modems have been retired.
I'm pretty sure that every modem replacement with an AR7 modem gained at least a 200-300 kbps maxrate increase and that would be enough of a difference to get the faster speeds.
Fighterpilot has a minimum maxrate of at least 2700 or he wouldn't be able to have 2496 speeds. He probably has something over 3000. If his line is quiet, he could qualify for 3008 speeds with a maxrate higher than 3400 (at least on a trial basis to see if it is stable).
A newer Modem may very well make no difference at all if the cap has to remain because of too high Attenuation.