Hardware for streaming question

I want to be able to stream video to my TV from my PC.
I know that there is loads of stand alone equipment that can do it but I already have wifi and broadband so Im trying to find the easiest way to do it. Also I dont want 2 separte wifi systems.
Heres the set up
NTL Cable TV (With built in Cable modem)
connected to a Wifi router. (The wifi router also has a USB and a LAN connection)
PC with Wireless adapter.
1.5mbps Broadband.
It would be great if there was something that could sit under the TV that plug into the LAN on the router and also into the TV

I really would appreciate any help.