Hdc3 18 Smaller box for more power?

like the title says. the hdc3 18 already has a box with it, it was mine from before and it turns out the box is smaller then what i thought the first time i owned it. it is 6.01 cubes before displacement, it has 2 6" aeros, the sub and small bracing, and after displacements the box was 5.30 cubes net.

I know alot of ppl will say that small for a hdc3, i was unaware due to i didnt build it originally nor did i even measure it until before when i owned it. well my friends measured it last night and yea it 5.30 cuubes. and power i was only pushing probly 6-700rms on it last year and thats when i got the numbers in my sig.

So im going to be using about 3.5k on the hdc3 18 and i would like to try the same box but im wanting to add alittle more port but that will take the box to 5.16 cubes net which is not that much smaller then the way it sits and im going to use more power. This will geared SPL>SQ

Thoughts? And sorry about the long rant