You think something like that would be too hard?Pioneer GM-D8601, 2 ohms: 500 watts x 1 chan.Daily 35hz is fine. I read up a little bit on port tuning but still don't fully grasp what it means. The simpler the build the better of course; I'm on a tighter budget.
If you want the plans please private message me with an email as it's easier for me to group all the drawings together that way once I dimension and explode the thing.
That's for up to rated power and as large volume wise and low as I could tune with no power handling loss. Probably too much enclosure, but will do well on your power.