One problem with this scenario (aside from the engineering concerns that bestbang has touched on) is the fact that most (or all) surround receiver users are likely to want to play some Dolby Digital or DTS material at some sort, at which point (1) 5 Stereo is no longer an option for most receivers and (2) your surround speakers' signals are going to your mains right along with the main signals, creating a very weird mix of noise.