it just means less power from the amp. if you bridge an amp to run the speakers it'll even out - so you'll get plenty of power and keep the amp cool. as long as you have an active setup i don't see an issue with 8 ohm speakers.

to elaborate - the reason an active setup will be better is so you can adjust for the reduced output from 8 ohm speakers.

the whole bridging thing is just to give them enough power. a 50Wx4 amp does 200Wx2 bridged at 4 ohms or 100Wx2 bridged at 8 ohms. otherwise an amp doing 50W at 4 ohms does 25W at 8 ohms. just be careful not to underpower the speakers or you may clip the amp trying to play them loud.