Okay, lets break this down.
1. You live in NYC (loud attracts cops). BL and HKS Ti is out. Putting the silencer in the HKS Ti is like....ah never mind....
2. You state 600HP, then you state 6766, which makes no sense. If you want to limit to 600HP, then get a Garrett GTX 40 Series. The 6766 on good gas is going to make 200rwhp more and on E85 even more. The decision on power defines which exhaust. If 800HP, then 4" plus.
3. If you don't want to drone out your neighbors and are truly satisfied and going to run 600HP, get the HKS Carbon Ti. Affordable, will support the power no issue, has the angled look you like, HKS quality and a cool carbon wrapped muffler. It's also affordable and not too loud.