The 2MB that you're contracted for is almost certainly a maximum figure. This speed will be degraded according to how many of the (probably) 50 other people who are in contention with you happen to be using the line at the same time.
On the subject of a wireless router, I use a Belkin router/adsl modem on my main phone socket, communicating with my (one) computer which has a USB adapter. Once the system is properly fired up, it's very good and my broadband speed is excellent. But initially it sometimes takes one or more restarts to get the adapter and the router to talk to each other. I have been told that I should have bought an IDE card, rather than a USB adapter - apparently they're much better.
By the way, don't imagine that you can plug an ISP-supplied free broadband modem into a router. You can't. Buy a router with an adsl modem built in.