In wall speaker suggestions

I am setting up a home theater in a 5.0 arrangement (no .1 for now at least). My mains are Thiel 3.6 and center is Thiel MCS1. For rears, I planned to start with some old JBL's then look at in-walls to save floor space. I'm concerned that in-walls won't stand up to the rest of the system. Any thoughts or speaker recomendations?
The best I have heard is the Linn Sekrets. They aren'r cheap but that is why they sound so good.
Since you already have Thiel speakers the best matching sound would come from the Thiel Powerplane or Powerpoint in-wall speakers. They sound very good.