The Xbox 360 and upcoming Ceton Echo are the only 2 current media center extenders.
If I were you, I'd buy a used Xbox 360 and invest in hardline ethernet or powerline ethernet adapters. Wireless is AWEFUL for HD video. Even with 450MBPS 5ghz wireless N and adapter, wireless throughput is too inconsistent. Unless the router is 10-20 feet away in direct line of sight, you're pretty much SOL.