I didn't like the sound of the stock setup on my limited. From what I can tell, it is the same setup you have, other than I was missing the amp on the tourpack.
So I invested in the Boom!™ Audio Ultra Boom!™ Bagger Kit. I like how she sounds now. Not nearly as good as a car setup when it comes to bass response, but the bass improvement alone was very nice. JCZ and a few others on here got to hear it. Maybe they can give you their opinion on what they thought as I really have no other speaker combinations to judge it against. My springer shall remain gadgetless.

The amp that came in the kit is the same as what you already have on your bike. Couple that with the bass booster kit and a flash to change your amp's frequency curve and it will fill in the lower end nicely. The stock amp has a low end frequency cut, wish I knew the exact frequency, but I don't. I think it cuts everything below 80Hz, and with the bass booster and EQ change, they allow it down to 60Hz. Just my thoughts. For all I know, the #s could be more 120Hz and 80Hz. But generally somewhere in that range.
However, I did audition your bike's audio setup when one was at my local dealer for a bit. The stock speakers just can't handle the volume without distorting. It was even worse on the limited without the amp. The upgraded speakers are very clean, the addition of the 4 tweeters helps a lot.
I'm sure whatever brand/combination you go with will be an improvement to your audio setup. It appears they only upgraded the audio on the RG and SG to some extent, but still left out some areas to have us go back and buy more stuff (common right

).
Since you already have the amp, I wouldn't buy the kit unless you have another bike you can use the amp on. Or if buying the kit is cheaper than the speaker kit and bass booster kit combined minus selling the amp.
As for the sound of the headset speakers. They sound OK, but not what I would want to use over a long period of time. I wouldn't be surprised if the low end freq. cut wasn't also affecting the headset, so even if they could produce decent sound over the whole range, it wouldn't matter.
Good luck to you if you decide to change it. There are so many options, it really is hard to choose.
One of the primary reasons I went with this kit is I got it installed within the 60 day period of purchase. So it now has a 7 year warranty. Did the same with a lot of the stuff I put on her.
