If this is going in the trunk then it's gonna be huge, I mean depending on tuning, but damn that's 6kw and 5-5.5 cubes net internal needed. I'd be thinking more along the lines of a wall or series 6th wall vs an aero port. If those are decent subs, then I mean that box probably needs to be massive to be like max efficiency of the woofers working. Tuning will make a big difference in box size with a large port, like you're probably looking at a box size externally of like 7 cubes or more to maximize those, just roughly speaking. You can somewhat get away with less port area in trunks firing rear or not forwards, but IMO not really with 6000w, like I just don't see that working well unless you have a very large aero and tune it to like 40 hz to keep the box small and the port length small enough, but that's gonna be peaky as hell and unload somewhat quickly, drop off on lows. You also can make the box too tall or wide or deep where 6kw worth of air pressure is having to barely squeeze its way in between the trunk walls and the box walls, gotta be careful there. And with firing forward and not sealing, you can run into cancellation issues with the trunk walls and box walls depth and airspace (airspace around the box inside of the trunk) acting like a t-line or a secondary ported box and phasing out certain frequencies. That can be a very big issue.