I am building a 5.1 surround sound system for my PC for gaming, watching DVD's etc. For the two front left and right speakers I am using my current XPRO 555 speakers, the backs I am getting are from ebuyer (quickfind code 126822) and I am building a sub from a guide on the internet. The only problem that I have is that I can't find a decent centre speaker thats in my price range (ie under £40). So I am thinking of getting another set of the back speakers and using them mounted on their side. Will this work and does anyone else have any suggestions or improvements for any part of the system?