The problems with running HDMI cables in-wall is that the in-wall cables tend to be thicker and harder to work with, some equipment can have range limits shorter than what you require and overall it can get a little expensive.  The simple solution is to transmit your HDMI signals over CAT5 or Cat6 cables. 
Monoprice delivers you an HDMI over CAT5/6 cable solution in a neat and tidy wall plate configuration.  These compact wall plate units utilize a pair of CAT5/6 cables and deliver pure, rich high definition audio and video.  Installation couldn't be simpler.