The most remarkable part of the leap from the Indras to the Eidelon Diamonds will be the tweeters. The diamond tweeter is absolutely phenomenal in its ability to convey unlimited high frequency with total cohesiveness with the other drivers. When optimized, it is totally clear, clean, and grain free. It does not overload, and it makes most other tweeters sound distorted. The tweeter makes music sparkle with energy and momentum that keeps one interested and connected to the music. And somehow, it is seamless with the entire presentation and does not draw attention to itself.
Optimizing the tweeter is a trick. If your cables or power are not optimized, you will her the grain in your cables and power. Any component or cable that is non-linear will accentuate the tweeter and make it less seamless.
I would second the Pass XA.5 series. You could probably do the 100.5 if you have a smaller room and don't listen to full-scale orchestral music. While the Pass is a key component to an effortless sound with palpability and weight throughout all frequencies, it is one part of a synergy that is necessary to really get the midrange and tweeter to the full potential. You can see the supporting components on my systems page. Finding components that work together on the Avalon has been a journey over several years. Luckily, the constant experimenting and trials have paid off.