There are several out there that are big money. The two you mentioned are definately up there in the $4-500 range. I did some looking around wanting (needing) to get some more airflow. I settled on the S&B system for a couple of reasons. First, it is half the money of those other two, second, it is an enclosed box, the AFE stage one isn't nor are some others, third, they have tested the filter to make sure it meets the dirt removal standards need to protect the engine. With AFE you need to get the proGaurd 7 filter and I don't know what Banks uses though they used to use K&N filters which I wouldn't touch. The S&B claims 40% airflow increase on a flow bench. It might not be the biggest gain out there, results are difficult to compare, but it more than meets my needs.
The other intake restriction is the air horn that goes into the manifold. I am replacing that as well with a part from CFM. Like the S&B it also claims a 40% increase in flow over stock. These two combined should more than meet the needs of my 100 hp box.
I think going with a mega flow intake and not replacing the air horn my be a little self defeating. Something to think about anyway.