I have it on my BPU car and I really like it. It's typical HKS quality (very high), fits perfect and has a nice deep rumble to it, especially for a BPU car (75 mm). It's quiet in normal driving, doesn't attract a lot of attention from the police and sounds great at WOT. A friend of mine liked it so much, he purchased one for his T04Z-equipped APU car.
Nice vid, Luke. BTW, the Hi-Power is a tad louder if you are TTC. It took a while, but I figured out that's why my buddy's car sounded just a little bit louder than mine when he was BPU (and TTC), whereas I am still sequential.
i have the Hi-power in my NA. its pretty loud during accel. and very inexpensive, $499 free shipping at evasivemotorsports.com (i ordered mine there) and it fits very flush into the exhaust groove in the bumper. im not sure about the HKS Silent though. im pretty sure you can by the inner silencer later if you decide.