yes and no
you shouldn't have any problem with the amp-rating difference. the Yamahas (help me here, Yamaha fans) are probably going to be a little more efficient, so you might have to use your amplifier settings to boost the mains a little or turn down the Yammies. that part is correctable.
the only thing you won' be able to correct for is "timbre". Each manufacturer (and sometimes different products within a manufacturer) wil be set to make a certain sound. When you mix manufacturers, sometimes the sounds don;t blend too well.
this will be the most noticeable on movies, in a case where the sound moves across the front. You may not have a smooth transition from the left speaker to the center to the right, for example when a car drives across the screen.
the odds are that it will be close enough that it won't matter. unless the speakers are way out of timbre match, you probably won't notice that unless you specifically listen for it. find a movie hat has a transition like that (for example the A-10 napalm run in Courage Under Fire) and listen for it. if there's good movement of the sound to match the movement on the screen, you're in business.
if there's not, ask someone else to listen to the same scene, without telling them what to listen for and see if they notice any issues. alot of times, you only notice a problem if you know what to look for. you may be able to help this a little by moving the center channel forward or backward from your listening position, while leaving the mains in a constant spot. it won't solve a major timbre mismatch, but will tune out some small differences.
as one of the members in here is so fond of noting, an enthusiast listens to the music, an audiophile listens for the noise
