Welcome to the fun. Are you looking for loud semi loud or keep it quiet. Do you want to stay duals or 2 in1 ??? We all have our favorite and we can be very bias. Little more information would help us steer you in the right direction or over whelm you with information Baaah ha ha ha ha
Tom is correct, first you need to choose style then you can start narrowing down your selections. 2 into 1 perform better, but some people don't like the looks.
welcome aboard! What seems like a simple question has a thousand answers. I would recommend attending some bike rallys/events. When you see/hear something you like ask. Anyone will talk your ear off about their bike. haha. Have fun!
If you're just looking to get rid of the the heat from the cat and gain a little performance you could remove the cat from your current head pipe and save some money. There are lots of threads on doing that.