Modem/router or separate switch

[gasdoctor]

Just wondering.

About to replace my router (dg834n)

I have a wdtv live wired to it.

Any benefits or disadvantages of using a separate wireless router/modem.

such as:http://www.overclockers.co.uk/showproduct.php?prodid=NW-117-LS&groupid=46&catid=1595&subcat=

with a gigabit switch

http://www.overclockers.co.uk/showproduct.php?prodid=NW-047-NG&groupid=46&catid=1626&subcat=

or

use a combined:
http://www.overclockers.co.uk/showproduct.php?prodid=NW-115-LS&groupid=46&catid=1595&subcat=

Cheers