Reading Spec Sheets

IMO, whichever amp better handles the complex load of a multi way speaker, typically will sound more powerful than an amp that can't, regardless of rated output into a 4 or 8 ohm resistor.

An amp will sound more powerful if it can double it's output into a 4ohm load or triple into a 2 ohm load.For instance the spec. sheet may read:40 watts into 8 ohms,80 watts into 4ohms,120 watts into 2 ohms.Many spec. sheets don't include that info. but a call or email to the manufacturer will provide you with that spec.

Look at the weight of the amp, in general, the heavier the amp, the beefier the power supply, the higher the current it can provide.

Yeah, my unscientific method of analysis is to look at the specs regarding power output at 8, 4 and 2 ohms, WITH ALL CHANNEL DRIVEN.

Just as an example, I have an Aragon 2004 2 channel amp that's as old as the hills. It's rated at 100wpc at 8 ohms and 200wpc at 4 ohms and weighs over 40lbs.

If you're looking at Class D amps, though, that's a whole different ball game.

Judging by power doubling, new Jeff Rowland Model 625 that outputs 300W@8ohms and 550W@4ohms is weak amplifier and that would be a mistake. Judging by weight, as Jmcgrogan2 suggested, is perhaps better, but there are exceptions. Amplifiers that have switching supplies don't require large transformers or big capacitors. In addition voltage is regulated. Mentioned Model 625 uses such supply but is very heavy (54lbs) only because of very heavy case. Power specifications are not that important since double power means only 22% louder. How is it measured? For how long? What frequency? Specifications can be some help but also can be very misleading. Amplifier with deep negative feedback can sound very unpleasant but will have great specifications.