So you are okay with paying $600 for a small HP gain and better looks but....
....don't want to spend another $400 to loose 30lbs, gain 10+rwhp, better handling, shorter braking, etc...etc...that you will actually notice and feel when riding the bike...
Sounds like you got raped on some slip-ons...
Tell you what, throw 30lbs of weight into a backpack and ride around for a week. Then ride without the weight for a week and come back and tell me it's not worth getting anything but slipons. A full system turns the machine into a completely different bike. Less weight and more power = WIN WIN!