I'm planing on buying some powered speakers that come with a subwoofer as my rear speakers. I was wondering is it a good idea to have another subwoofer on the rear channel? Surely it can't do any 'harm' to the noise because the lower frequencies will be directed to the main sub but some of the lower rear sounds will come thru the sub. The reason I wanna buy the speakers with a sub is that cheap speakers which I'm buying as rears, don't sound all too good but with a sub they sound fine. I can't afford to get myself a decent set of rears because I don't have the monye to buy an amp. So powered speakers is the next best thing. I know you can have stereo subs and things like that but I havne't heard of anyone doing this.