1. Arata: quality; power gains--most and broadest gains; quality; weight (saves 14lbs over stock); price.
2. Akra: same as #1, but more top-end oriented power gains and more expensive for full TI;
3. I like the looks of the Yosh full system with the shape of the can--not sure about the power.
4. Whatever you like best!
Just be forewarned, you will bet about SAE 7rwhp, 3rwtrq with the system, pc3usb and a map. $$2k or so.
I suggest a pc3usb and custom map on the stock system first.