Unless they've changed things for 2005, all D-1 Spas (except for the Bay series) come with a light that you can change the lens of to get different colors. Each spa comes with a Red & Blue lens. You can get an optional LED lightfor all of the spas. This has a color wheel providing many different colors.
The Lotus bay has a Bioform recliner chair with the sequencer. The Chairman II and the Diplomat each have an Ultra lounge. The Diplomat also has a "hers" lounge. The Chairman II has a sequencer in the lounge. All Three are great spas, w/ different layouts. Definilty Wet test them if possible. I would also consider the 2005 Californian, as it has water features, lights, and a nice lounge seat as well. D-1 Completely redesigned the Californian, and I have to say that it looks awesome now. Personally i hope they give the same treatment to the nautilus as well in the future.
Jason,
Store Manager for a D-1 & Caldera Dealer