Virgin Media broadband Modem replacement

I live in England and I have a virgin media 20mb cable internet connection.

1)Would I be able to replace the standard modem that virgin gave me when i signed up with a netgear (or any other manufacturer) modem?

2)Would it improve my internet connection at all?

3)Which modem would be best and how does it differ from the other models? i.e. model numbers: CMD31T, CME31T, CM232, etc

Netgear products:
http://www.netgear.com/Products/RoutersandGateways/Modems.aspx

Amazing graphic representation of my setup:
http://www.geocities.com/sam_garner_1985/Netgear.bmp

I don't think its a hard question but i asked the same question to netgear pre-sales technical help which was completely useless i might as well have asked my cat as the answer would have been just as helpful. They told me the model numbers i quoted were not netgear products (see the above link) and then when i convinced them that they were netgear models they said:

 ...this is directly copied and pasted from there reply...
I profusely apologize for the inconvenience caused. The model no: CMD31T, CME31T, CM232 or DM111Pv2 these are all wired modem and you will be able to access the internet only with one computer.

.....yeah because thats what i asked ...hmmmm i think someone needs a bit of training, maybe they should start using this website. Anyway enough with my rant... anything more helpful than the above would be greatly appreciated.


Thanks, Sam