Specs are down at 70htz mate so theyre not going to have an issue at 80htz bass response wise really.
Depends if you're using a sub aswell really in which case I wouldn't go below 100htz & let the sub handle anything below.
If you're not using a sub I'd take them right down to 70htz & see how they sound.
With two 4 inch woofers I think Audyssey is correct to set the crossover point higher than usual.
If you set it lower the rears might not sound as clean or play as loud as you need them to. It would depend on the room.