I have been unable to get my hands on a pair of KSP-S6 surrounds for my KLF-30's. If Klipsch offers no other choices,what other types/brands would be close timbre match?
I think for surround, the timbre matching is less critical. But, I also think it would be a good idea to stick w/ Klipsch for that trademark horn-loaded tweeter sound. Things will be more cohesive that way IMO.
Even though it's recommended by Klipsch, the KSP-S6's aren't timbre matched for the Legend series. If you have the space, I'd look for KLF towers, the KLF-10's are going cheaper on ebay than the KSP-S6 I recently saw. If towers are out of the question, I'd look for a pair of KLF-C7's. If you can't find those, then I'd look towards the RS-7's.
I have used KLF-30's for several year's now using Klipsch KG-3.5's as surround's and when I upgraded to 7.1 I added KSP-S6 as my side surround's. That worked great until I joined Klipsch.com and read about how using KLF-30's as rear surround's was the best upgrade. You have the choice between KLF-10's, KLF-20's, KLF-30's, and either the KV-4 center, or C7's. For the ultimate realism, I would recommend KLF-30's as your rear surround's or the any of the KG series speaker's from the same era of the Legend line.