Any Cablelabs certified DOCSIS 2 cable modem will work.
On a HFC (hybrid fiber coax) network, the available bandwidth is all shared among all the subscribers on that HFC leg. I would take the claim of 5Mb/s with a grain of salt. Plus if you have to upload high BW content, an HFC upstream is going to be a big bottle neck.
With DSL, you are not sharing BW on that DSL drop. The 3Mb/s to 5Mb/s comparison may not be apple to apple. With DSL though, how much BW you get depends on how far you are form the CO. Laws of physics whether ADSL or on ADSL2+. I do not know if you are on an ADSL or ADSL2+ circuit. The majority of BB consumers in France are on ADSL2+ so folks can really get 16-20Mb/s.
To a large extent, all BW are shared. From that fiber node on an HFC or the DSLAM, the trunk BW is all shared. How much BW you get depends on the network engineering of how many subscribers on a given Gigabit Ethernet trunk. In Japan and Korea, this engineering is very conservative (very few customers on any given trunk). FTP at 50-70Mb/s in Japan is basically common stuff, but that is on a fiber to the home. A 100Mega service is very common there and dirt cheap relative to what FIOS charges.