For just internet streaming? You wouldn't.
But you do need to understand that "108 mb" number is BS. So is the 300mb on the newer routers. Real-life sustained throughput on a G router for example in the 15-25 mb range. Real-life for most n routers is in the 25-40 mb range.
Both remain plenty fast enough for internet streaming (assuming nobody else is doing anything on your network of course- if your kid is wirelessly streaming something to his ipad while you try and stream too, plus your wife is streaming pandora in another room wirelessly, your G router might be sweating a bit).
But neither G nor N is adequate for local network streaming of high bitrate blurays for example.... which is why wireless kinda sucks for that.... (wired being best, something like powerline or MOCA being next)