You have to look at what wood you want to use... good wood cost a pretty penny.... You have to look at what speakers you want... good speakers cost a decent amount... You're right in saying that you'll want a closed back if you want a good bottom... Closed back cabs will require you to have some port holes...

I guess for me... If I put myself in your situation. I would weigh the time and money it's going to cost me to build a cab versus the ease of making a good one time investment. If I were you I would just look for a decent cab that's already out there. The one time investment would be more useful and time saving for me... i don't have the time to invest in building something like that right now... I don't know how you feel about just buying a cab for 400 bucks versus spending 300 bucks building one.