Upgrade Thiel CS3.6 to CS6??

I am thinking about bidding on a pair of Thiel CS6 speakers in bird's-eye maple, and would like some input from those of you familiar with these speakers. I have owned a pair of CS3.6's for seven and a-half years and I've been generally very pleased with their sound. Can anyone out there tell me what I can expect to gain in terms of sound and performance by upgrading? Do the CS6's have bi-amping/wiring capabilities? My current amp is a Mark Levinson No. 23.5 which is what I plan on using should I get the CS6. I'd imagine that should be adequate as it is capable of delivering 400 WPC continuous into a 4 ohm load. I also have a Mark Levinson No. 27.5 that could be used in a bi-amp setup if the speaker is capable. My listening preferences are extremely diverse and include rock, folk, classical, jazz, "adult alternative".

My other concern would be room size and the restriction to a fairly near-field listening position. My room is somewhat odd in its layout. The dimensions are: 13 feet wide and 22 feet long. The caveat is that the room opens into a foyer and is interrupted by a staircase that cuts off about half of the back wall. In other words, half of the back wall is 14 feet from the front wall and ends at the stairs, while the other half of the back wall is 22 feet from the front wall and extends into the foyer. I hope that made sense. Because of the staircase and foyer, I must sit about 8 feet from the front plane of the speakers. I keep the back edge of my CS3.6's about 30 inches away from the front wall and the center axis of each speaker lies 40 inches from each side wall. The speakers are 75 inches apart when measeured from the center axis of each. Is my room too small to accomodate the CS6's? Please keep in mind that I will likely be moving into a different home in the next 1-2 years (with definite plans for a dedicated larger listening room), so I could live with the current suboptimally sized room temporarily.

Thanks to all and happy listening!!

Mark