I actually know what you're talking about!! I have comcast, and on the modem I was getting 6mb down, but on my Netgear wireless router I could only get 3mb. I bought the latest revision, and it still did it!
I looked around, and honestly I don't like any of the routers out now. I'm not too fond of Netgear after this thing, I've had too many friend's with D-Link problems, and the new revisions of Linksys are either too pricey or not good. If I had to buy a normal router, I'd say give Linksys another try. Do some research on your needs and what people have said.
I didn't like any of the retail options, so I build a smoothwall router from an old machine. Best thing I've ever done. Simple setup (once I read the install guide) and super fast. I now get 6mb down and full up speed on all my PC's, even wireless.