The Beolab 9 is based on the Beolab 1 chassis. Therefore the treble and midrange use AB amplifiers. To make it all ICE and digital would have impacted upon the Beolab 5 and made it more expensive.

I think the 9s sound better than 3s and a 2 as they sound more integrated. The bass, certainly for music, is better at higher volumes. However I do think £5000 is a lot. This sounds Irish, but I would actually get the 5s instead as the difference between the 3s+2 and 9s is relatively small but the 5s are streets ahead. Part of that is the superb set up technology of the 5s which adapt to your living space in a way the other speakers cannot.

I wouldn't make decisions based on technical specs - go to a dealer and here the speakers you are interested in for yourself - that way you can find out the differences!

 Personally I'd go for lab9s !
 

@Razlaw: Why do the 3s and 5s use ICE power and the 9 does not, except for the400 watt  bass?

 
According to an ultimate audiophile acquaintance: The Class AB amplifiers used on the midrange and top of the BL9s deliver a truer, more audiophile sound than would a 3xICEpower configuration. ICEpower amp's deliver amazing power at a minimum of heat produced, but trained ears can hear a faint audio artifact from Class D amplifiers in the mid and top that was gotten rid of with the AB amplifiers in the BL9s. This was also mentioned in an article reviewing the BL9s back in February of this year. (Fidelity; 2/2007).

ICEpower is perfect for the sudden power requirements of a hard working bass driver though - where you do not get this audio artifact.

You're asking a valid question, as it appears that B&O is adjusting its use of ICEpower with the BL9s. 

I found the lab 9 produce much more realistic in midrange and high frequency, especially in vocal, much more transparent and the bass is more precise compare to lab3+2. The bass is adequate for typical music listening, but i felt there is still need for a subwoofer to have a true cinema experience, this may change when they update the software on Beovisions, but when I demo them with lab1 setting, they don't go very low, with lab 5 setting, they started to have distortion.

 Like other members have suggested, go and have a listen at your dealer, only your ears know what is good.