cable modems

Hi

I have a cable modem that is about 7 or 8 years old its a 3com us robotics.
that came with my rcn cable company. rcn as since been pushed out by suscom who has now been pushed out be comcast.

long story short I am supposed to have a 6mb download and 386 upload. at first comcast was telling me my records were never transfered over correctly that is why dslreports speed test only give me 2mb download and 200 upload

they have since corrected there records with no affect on my speed and now they are saying i probably need a new cable modem. Are the newier cable modems faster? if anyone knows anything about it I would be glad to hear what you have to say. also I do have a linksys router wireless g with 4 port switch model wrt54g. Thanks

Eric