Wattage is a meaningless measurement. What’s more meaningful is the efficiency. JBL are noted for being very efficient. The 180 wattage rating means they can handle 180 watts RMS (continuously). What you may find is JBL’s are too loud and you may need to adjust balance.
The thing you need to worry about with these systems is they are designed using the correct amps/speakers and placement for maximum performance. Replacing a speaker with a different one may effect the overall sound.