Broadband-USB Modem V ADSL Router

I have a Dimension 4550 with a broadband internet connection in the UK, using a USB ADSL modem.  I'm beginning to run out of USB ports and since I'm thinking of buying a digital camera I was thinking of getting an ADSL router to use to connect to the internet, freeing up one port.  I was wondering if this would give any sort of performance boost to my internet connection since an ethernet connection between the modem and the computer would be faster (I imagine) than a USB one.  Also, can anyone reccomend a good combined router and ADSL modem?  I'm not bothered about the number of ports on the router since there's only one computer in the house and I don't anticipate getting another.

Thanks for any ideas.