I agree with this man! Although I might be biased...
Rodny, whatever you do decide, I'll be following along closely to see how yours turns out. 68 Litres... what's that, about 2.5 cubes? that should give you a great sounding sub. My volume constraints will definitely impact my end results, but I wanted to build something smaller this time. I think with a sub that size you should easily be able to fit the driver and port on the front face. What are you porting with, 4 inches?
Did you have any design ideas, or are you open to any kind of suggestions? I guess it would depend on what the rest of your room and speakers look like, and how important it is that the sub mesh into the decor. What about finish? Wood, or paint? Standard big black box? (I'm now living vicariously through your project).