Thanks all for the helpful and clarifying replies! They all have good points. My room is 3*6 metres with a high roof at 4 metres but I usually listen at moderate levels and seldom at dynamic music. Also sitting pretty close. As a father of two the need for party-levels is reduced! According to Stereophile, the impedance of the Proacs seems to be acceptable for PETA (People for the Ethical Treatment of Amplifiers) :-), and I also like the sonic signature of tube amps, so I will go for the Proacs.
/Chris