[animaltrouble]

Don't run your 4 ohm amp with 2 ohm speakers - the amp will need more power to drive the speakers at higher volumes and yes you can fry the amp, it also won't sound as good as 4 ohms. Also you need to fool around with the wiring if you were going to keep the 4ohm tweeters and replacing the woofers with 2 ohm ones as you have a mismatch, whatever xover is involved by default has one ohm rating. There's really not much to be gained, if you want to upgrade the woofers then stick w/ 4 ohms.