I actually tried a pair of 5200's as rears instead of my 7000s a while back when I was considering going 4 x 5200s sides + rears. Resulot was simple - I stuck with my 7ks. The 5.2ks are good speakers, but not like 7000s. Since way back with the original 5000s, I've always thought that the 5k/5.2k design is compromised in the upper bass/mid range due to the driver layout. This is one areas that the 7ks do quite a bit better, as well as having a lot more bass punch (but more controlled than the (in)famous 5500s).

my 2 p's worth, which may not be echoed by others.

Andy

System 1: Control 15, 818v3, 800v3, 861v6, DSP8000SE, DSP7200HCSE, DSP8000.2, SW5500, HD621, 650BD, SkyHD, Radience XE, TH65PF12
System 2: MS200, 5200
System 3: MS200, F80
Sooloos: MD600: 2x3TB
On the move: Explorer 2, B&W P7W
Bedroom: F80+i80