Such difficult acoustic problems seem relatively rare. It does seem to be at conflict with their long standing advice on active operation. However, the IXO offers a different upgrade path for owners of Credo based systems with lower specification amplifiers and a relatively cheap solution for those facing room acoustics problems. Using mono amplifiers requires one amplifier for each frequency band in each speaker. When using stereo amplifiers each channel can be used separately and so half as many amplifiers are needed.
Active operation can bring major improvements for many reasons.
Active systems also allow the range and level of frequencies going to each driver or set of drivers to be adjusted and can be used to tune the system to work in rooms with difficult acoustics. It is frequently possible although the results are mixed. Generally speaking going active with Naim amplifiers is a lot easier and more successful if you also have Naim speakers. Firstly, your speakers must allow the passive crossover to be removed and have separate terminals for each driver. It may also require some adjustment of the active crossover for which there may be an additional charge from Naim.