The consensus on adding EX is that it's best to have dipoles to the sides and a pair of direct radiators in the rear. The method that I prefer is to run a Y-connector out of the preamp outputs of the rear channels. Run one end of each Y into the amp powering the dipoles. This will give you normal 5.1. Now, run the other Y into the inputs of a Prologic receiver. The center channel output of the receiver will contain the rear center channel information. This will give you the benefits of EX without the drawback of everything collapsing into the rear center channel.
The other route is to get a CircleSurround decoder from AVScience ($299) and run everything through it. It has a control on the front which controls the amount of center channel information to prevent the rear soundstage from collapsing. I have heard, however, that the CircleSurround unit introduces some noise to the signal but many people are very pleased with its performance. See the latest edition of Widescreen Review for a review. Having said all this, I also have all the equipment lying around but haven't got around to hooking it all up. I'd be interested in your thoughts once you get it running.
The other route is to get a CircleSurround decoder from AVScience ($299) and run everything through it. It has a control on the front which controls the amount of center channel information to prevent the rear soundstage from collapsing. I have heard, however, that the CircleSurround unit introduces some noise to the signal but many people are very pleased with its performance. See the latest edition of Widescreen Review for a review. Having said all this, I also have all the equipment lying around but haven't got around to hooking it all up. I'd be interested in your thoughts once you get it running.