Hi ranidweik, and welcome to cruise-chat.com!
I was on Regal Empress several years ago before she was operated by Imperial Majesty. I love the ship and am happy to answer any questions on layout, cabins, etc. Cabins S6-S10 are very different from each other, though. For instance, S10 is a suite, whereas the others are outside staterooms of various sizes. Also, I'm not sure what you mean by ecl level... but, if you are indeed talking about Sun Deck, that is far preferable to the lowest outside cabins on A- or B-decks.