IS noticeable, and at the new price it is definitely worth it. Somewhere I put a post in here on that as I upgraded all 4 in my RM (waiting on saddle bag lids for the rest), but it made a HUGE difference in clarity and volume.
+1 on powerband being better, stock is not bad but powerband in my opinion is clearer. I got mine from cheapcycleparts.com saving about $200.00 over the old price. I know Indian reduced the price just not sure if there is still a savings going with cheapcycleparts.com. The trick is to find the part number of the powerband speakers by downloading the installation guide and order 2 from cheapcycleparts.