I have the same problem of only 10mbit through the router (SMV7004VBR), through just the modem (NTL200), approx 17 to 18.
Left a post on another part of the forum and a kind gent pointed me to a website that stated that my WAN port on the router was only rated at 10 base T and not10/100 base T as in the instruction manual.
After 3 very confusing calls to SMC (India me thinks), they told me that it was indeed only rated at 10. So I am off to get me a Linksys WRT54GS, although I will only be using the wired side of it, patrners son can use his laptop