Ok, in a nut shell the CT is smoother, but still fully retains the Vandersteen's 'suddenness". The staging and imaging are just a tad more accurate. The changes are subtle. I'd say a 10% gain, but when you have such a highly revealing systems, it's worth it to most people. The gains are at the top end, but strengthen the coherence too based on my opinion. Magic is the word I think of when listening to them set up correctly in a good room. I've never heard them sound their best though as they keep getting better with better equipment. That's what I love about Vandersteen's. They give you what you pay for in the rest of your system. His home made Carbon Fiber tweeters are just very special. I have heard the new diamond and beryllium drivers from others and they just don't hold a candle to the carbon fiber drivers in my humble opinion. I know it's about implementation, but those B&W diamonds will spit on difficult passages and to me are fatiguing. I'd rather speak with the salesperson after 3 minutes of listening and that's with their top rated gear on them. Aways excuses from B&W fans against me, but even the sales person as the last store agreed with me and said he didn't like the new 803's either. With the Ceramic tweeters that the wood and my Treo's have you get detail out the wazoo as well as a sweet enough high end, but I know what's out there is better and I want it.
That's why I'm selling my Treo's right now because to me the Quatro is the best value in the line as it's much closer to the 5 CT than it is the Treo CT or regular Treo.