Sdcvo,
The question was "should I?" and IMHO I'd say yes you should. I'm not sure which way you are leaning but as I ahad already added a 2 channel HW amp, he speakers and tweeters up front, I decide to add to my system with the Harley lidas, 2ohm 5x7s and there own (another) 2 channel amp to drive them. (used hogtunes 70.2 amp for rears)
In the end after all the ene gy and money painting the lids etc etc it actually sounds great. Probably not as much bang for the buck had I started from scratch, but I'm no audiofile, and the sound is much fuller and richer and yes louder even at speed. My wife rides herself ona sporty and she says she doesn't need a radio... She can hear mine as we ride.
Tif2 (rich) was abig help both technically and motivationally.
Had I to do it from scratch I likely would have gone with one big 4 channel amp I guess... Would take up less space in the fairing... But at the end of the day I have no complaints at all with the Harley speakers and lids...the difference is huge compare to 2 speakers.
If your interested in more info let me know and ill post a list of parts.