I've got the J&M 7.25" Rokkers installed in the bottom as an upgrade to just having the Rokkers in the fairing and rear with the 250W amp.
Frankly, it's a total waste of money. Originally, J&M guys installed the lowers running off the front channel of the stock HO amp and the 250w amp was running the fairing speakers. You couldn't even hear the lowers.
So, I ended up rewiring the amp to run the fairing and lower speakers in series off the 250w amp, and just the rears of the stock HO amp, and while you can barely notice them widening the sound stage a bit with the motor off, you just about have to put your head down to the tank to get the full effect. If I stick socks over the fairing speakers, you can definitely hear them, but in the normal seated position, the fairing speakers totally take over. As a matter of fact, if one of the lowers cut out, I'd probably never notice it. The fairing speakers are just closer and have a more direct path to your ear. Perhaps on a totally custom install, with more power on the lowers, it might work out, but with the same power as the fairing speakers, it's just not the hot ticket, imho. Looks cool, but that's about it.
So the net effect is, spend your money on better speakers or amp, and you'll be way ahead.