yeah, I won't dwell on it but after all this we need to go back to my original post which I deleted
The ambit 256 is a single channel modem which can only do ~24mbits maximum so even if there was a 70mbit config file for it (the file that tells the modem what it can do) you would still only get 24mbits. I had the ambit 256 when I was on 20mbits many years ago and moved up to the ambit 300 (what I got confused with) which is a 4 channel modem (good for 200mbits) when 50mbits first came out and I kept that all the way up to 120mbits. For 200mbits plus you need an 8 channel modem (which means a shub) purely for the speed but VM like everyone to have them these days because they are a combi modem/router which makes it easier for VM to troubleshoot if you have any problems.
If you have simple needs then the shubs will suffice but depending what you do on your network (and especially if you are used to having your own router) I would consider investing in a newer and up to date router to compliment the shub in modem mode.