Chaos Marine Bikers - What am I doing wrong?

Here is one of the first models that I did back when we got back into 40k. I was really excited about these guys so I bought up a few boxes of them and have a little warband of 6 of the guys. I played several games with them early on but they just never performed for me.

The way I would run them was pretty bare bones - 6 guys with an icon of Chaos Glory. Looking back at it I realize that I didn't have any punch in them. So my question to you readers is what do I need to add to make them have the punch they so desperately need?

My best guess is to add in a few Meltaguns and a champ with maybe a Powerfist. What do you guys think?