What might help is knowing what type of files you are hoping to stream wirelessly, in particular their bitrate.
I regularly play 720p MKV files with bit rates up to 9,000 Kbps. I connect wirelessly using a Draft-N Belkin USB adapter to an AT&T ‘G’ router (2WIRE 2701HG-B). I seem to get max strength signal (at or near 54Mbps). For me, a 54Mbps router is fine.
If you’re playing higher bitrate files, a wireless ‘N’ router might work but if your share files are on the laptop, it could become a bottleneck with that network card. If you upgrade your router, get a matching network card for the laptop.
Something else that may be worth trying is a media server on the laptop (I’ve had good experiences with TVersity). People have reported being able to play higher bitrate files than normal when using a media server. It’s free and will only cost you the 20 minutes or so it takes to set up.
If that fails, you’re back to looking at a new router.
My only experience with ‘N’ routers is with TRENDnet’s TEW-635BRM (when my previous AT&T 2WIRE died). It was easy enough to set up, had some nice features and connected to my laptop at 130Mbps. Unfortunately it had buggy firmware and would disconnect and forget settings. Put me off TRENDnet for life.
WD have a page listing supported hardware here:
Make a selection from there to have a higher chance of it working nicely with the WD TV. ;)
Having said all that, cable is king for streaming stability. If it’s possible, it’s the best way to go.