A little while ago I moved up from a 2x45 watt Quad 303 to a 2x140 watt Quad 606-2 (both driving relatively inefficient Quad 2805s in a pretty large listening room). The biggest benefit was a cleaner and more dynamic sound. The old Q303 had clearly been asked to do more than it was made for. It has persuaded me to put a pair of 2x260 watt QMP monoblocks on my wish list.
Unless you are into boutique amplifiers, power does not necessarily cost much. Take a look at the excellent Pxx00s series of Yamaha Pro Audio amplifiers. The series has now been discontinued, so with a bit of luck you can get a real bargain. See here for an exhaustive test of the 2x350 watt P3500s: http://www.homecinema-fr.com/forum/amplificateurs-de-puissance-haute-fidelite/mesures-ampli-yamaha-p...
Unless you are into boutique amplifiers, power does not necessarily cost much. Take a look at the excellent Pxx00s series of Yamaha Pro Audio amplifiers. The series has now been discontinued, so with a bit of luck you can get a real bargain. See here for an exhaustive test of the 2x350 watt P3500s: http://www.homecinema-fr.com/forum/amplificateurs-de-puissance-haute-fidelite/mesures-ampli-yamaha-p...