I have my pair of CS3.6 for over 9 years. Prior to that I had a pair of CS2.2 for 5 years. I've been contemplating about upgrading to a pair of CS6 for the past 3 years. But every upgrade I had in the past 18 months brought the performance of the CS3.6 to another level with noticeable improvements! First I replaced the preamp from an ARC LS-2B Mk II to an ARC LS-25 Mk I with GNSC reference level mod. Then I replaced the Siemens 6922 tubes with a quad of white label Amperex 7308s. Recently I replaced the Mark Levinson #333 with a Pass X350.5. I've been just amazed how much improvement I got with each "upgrade".
One of the must haves tweaks for the CS3.6 is the Sound Anchor bases for these speakers. I've had them since day 1 because the dealer recommended them. But recently I took them off for a friend to try them. He was so amazed of the improvement he heard, he immediately ordered a pair. (these are the older model, not the ones currently offered on their website, but you can special order them.) My friend had been trying out some expensive interconnects, speaker cables, and powercords over $2k. But he said that these bases turned out to yield the biggest improvement. I think they run for under $300 a pair. They tightened up the bass, give more "weight" to the sound, and have a more three dimensional soundstage.
I'm still searching for a new pair of speakers. But all the candidates on my short list all cost over $12k a pair. And I'm afraid that I might regret selling them after the fact.
FrankC