I have heard the 2.0 cores on a identicle bike at Worth HD in KC, MO. the sound differance is not noticble. i have the 2.25 Power Core SD.s on mine...I have no packing in mine...i might put some in to see if it helps....i wont know till i get my TTS Tuner and xpipe which ive waited for over 8 weeks, and get the cat out...i have read alot of posts .... and heard alot of bikes recently,i am looking for a sound that is deep, and rich ....but not enough to drown out the stereo system...a delicate balance....(loud is easy) i heard a stock 103 at Gails HD in Kc with stock headers and cat still in, with CFR slip ons....Wow talk about a rumble....I never even considered CFRs till i heard them in person.....i dont really like the looks of them was going for stock look with added performance and sound, which i believe Fullsac has nailed( not to mention make bike run cooler )...I have invested alot in this bike which i love dearly....i beleive i will get the TTS and x pipe on and experiment with differant slip ons untill i get the perfect sound...chit this might get pricey!!!!! i