Maybe by a degree or so, but probably not excessively. I've the same CPU and cooler, and my idles are at about 28 - 30 degrees C, so you're doing well there. Also, bear in mind (and I'm not trying to patronise), that you can't cool cooler than the ambient. 23 deg C is very reasonable, guessing your normal ambient is probably about 21. So when you add in an enclosed space, limited air-flow (relatively speaking) and other components giving off heat, you might not improve any.