I think it's funny that you guys think bigger is better....
For the money, the JDM ITR header is a great piece. If you're willing to do a little work to it, it's even better. Welding the outside and opening up the exhaust ports will increase flow similar to the Mugen spec header which is about 2x the price.
However, I have found that 4-2-1 headers have more useable power over the 4-1 on a stock or near stock engine.
Check "the great header test" on HT.com I think you'll find the results enlightening.