I like my Rush 2.25's, but they are the only ones I have tried, and they are loud. They sound good to me. You can get them at a resonable price on ebay.
Like someone mentioned earlier, the Kuryakyn Crushers have the best deep and throaty sound, are loud when you want them to be and are a high quality piece built to last. I put a set on my 2007 Street Glide and have not been sorry. I am saving for the true dual pipes to go with them but am wondering if I will even bother. With the XiED's and a K&N air filter, the bike sounds and runs great. No black boxes or dynos for this guy!
One other nice touch, they look really nice and are just different enough to stand out in a crowd where everyone has the same 2 or 3 brands.
I just installed Fuelmoto's Jackpot mufflers onto my '07 FLHX. Without a doubt the best sounding mufflers I have ever had. They have a low deep rumble at idle and cruise until you twist the throttle than they scream. Kind of sound like glass pack mufflers from back in the day. Fuelmoto also emailed me a custom map for those mufflers. Bike runs best it ever has. Mufflers cost $299.99 plus $18.00 shipping.