Don't waste your money..... They are worthless over 30 mph. They may be better with a hardtop, though. Anyway, just focus on putting good speakers in the overhead unit and you'll get all the sound you need. By the way, most speakers are marginal at best in those units so be prepared to select some decent replacement speakers. Nonetheless, the overhead unit is the way to go, especially with a soft top.
Cheers.
I gotta agree with some of this and disagree with other parts. I have those Polk Audio plate speakers (50W RMS) and and Alpine head unit (18W output), and I could hear the music with only speakers in the stock location, doorless and topless at 75mph if I turned them all the way up. Once I added the skypod and two more 4" Polks at the rearview mirror I could hear easily! I've adjusted the fade (the speakers at the rearview mirror are my "rear" speakers) so the dash speakers get about 70% of the power and the balance is amazing. I'm looking at the Alpine Power pack amp (boost the power output to the speakers to 50W) and a small powered sub to fill in the lows and complete my sound setup.
Maybe I've got a little nicer (more expensive) equipment than some, but I can promise you you'll be able to hear. I doubt my Alpine headunit puts out any more power than other head units, but I got it for a bargain at $95+$6 shipping off ebay. Same goes for the speakers... my current investment is around $250... with the power pack and powered sub, I hope to not be beyond $500 total
Synopsis:
-Stock speakers suck, if they even still work
-decent aftermarket speakers at the dash location and head unit *should* allow you to hear the music regardless of speed or "type of top"
-It is a Jeep, and its doesn't have the acoustics of a sound room, you're just trying to drown out the creaks, groans, clunks, pops, ticks, clanks, and so on with music of your preference.