An open pipe will lose you some in the bottom end but will open up the top end. You will have to retune (Re-jet if carbed) to keep it running correctly and it will be a lot louder than even the most rudimentary can.
If you want a basic can that won't cause big changes in the way the bike works, take your bike to Meineke.
I know, people are laughing, but here's the deal. Meineke is a muffler place. It doesn't much matter what the pipe goes on, the one near me will work on it. While they don't carry motorcycle specific mufflers, they do have mufflers that will work. For instance, Meineke carries a resonator that is 12" long by 3" diameter and can custom fit pipe to make it work for you. The resonator is $25 and whatever they change to bend and weld some pipe... still a lot cheaper than some of the "performance" exhausts out there that are, under the pretty carbon fibre appliques, the same damn thing.
I have been through half a dozen exhausts on my bike, searching for that perfect look, sound and performance. the local muffler shp has done the welding on the last couple and I have zero complaints about thier work. In fact, they were stoked and the mechanincs were arguing about who got to work on the bike because it was better than working on their 50th Eclipse.