JBL SP5 or SP6 as Rears

I have a similar situation and initially went with the SP6's in the back wall of my living room. I never was very pleased with the sound that came out of them. I recently replaced the SP6's with a pair of JBL HTI8's. They seem to be much better, to my ears at least. They seem to be a better timbre (SP?) to my JBL S38 fronts. The transition around the room now seems much mor seemless. The HTI8's definately have better tweeters than the SP6's have. Best of all the HTI8's are only slightly larger than the SP6's. While I had them out I stuffed part of the wall cavity above and below the speaker with fiberglass insulation. I don't really know if the difference in sound was entirely the speaker change or adding the insulation or both. Doesn't matter though as I'm currently (currently being the operative word) pretty happy with the sound quality.

Keep in mind that in-wall speakers are rarely (if ever) the best choice. In my case the choice was dictated by the layout of the room and more importantly by the wishes of the decorator (the SO).

I think that if I were doing a bedroom mini-HT I'd more than likely go with the SP5's. Simply because I'd be more interested in saving a few bucks on a system where I wasn't doing my most critical listening.