I thought about the cheapest option is to get two WRT54G, Flash them with DD-WRT and Custom Parabolas but I'm afraid that they won't be efficient for HD streaming, that's why I'm leaning toward the next gen, which is the WRT160NL and do the same. However, they are running on 2.4ghz and can very well be interfered.

Sherwood - How should I setup the Nanostation M5? Pretty much all it does is a Bridge with Hi-Gain, 5Ghz Freq? I'd still need a Wireless N router and/or a GbE Switch @ my parent house for them to get the max speed via wireless?

That seems like the best bet since it won't be interfered by any other 2.4ghz signals and can establish 150+Mbps bandwith, which is more than suffice for HD Multimedia Streaming.

Please advise,

Thanks,
Kevin