Hey PtDemon,
Thank you for the Props on my set up. I still have some more things I want to do, but for now just mostly more cosmetics. It still doesn't quite hit like I want, but I am maxed out for this box so I will need to redo everything to get more out od it so.
As for materials, like you already know, MFD is cheapest, and easiest to work with. Acrylic is cool looking esthetically and to me will give you a slightly more refined tighter sound over the MFD. Fiberglass is also very cool looking looks wise, but like with a lot of things in the custom world, it takes practice to get good at working with it. Also depending on how complicated you wanted to go with your layout, you need some decent wood working skills to make a more complex cabinet out of MFD, then stretch whatever material of your choice over the box, or if your going to paint it, get ready for mega sanding, sanding, and more sanding, and then some pretty serious money in prep and paint. To give you a ballpark, if I were just going to prep and shoot it with a standard base / clear, I you would be looking at around $300 - $400, and that's without going into all the filling, sanding, and prep to get a good surface to work with.
So, MFD = cheap, and easy but you are limited in making an elaborate cool looking set up, and some upholstery skills are helpful.
Acrylic is good but you need to really make sure you allow for ample support of your structure to support the weight of your subs, and allow for the vibrations or you could easily wind up with cracks in the material. On a good note, their is no need for upholstery. You can also use a combination of Acrylic and MFD to help support the structure, and still make it look cool. You can use acrylic for a face of your box, and then use some mirrors, and back light it for a really cool effect.
And Fiberglass is a ton of work, and most expensive, but if done right, has a way cool look, and most complexity to it.
As for a sub floor, its pretty easy to build. The big thing if your going to put amps either under your floor, or like me put a two tear set up so you can put multiple amps under, you just have to get your dimensions right for a nice clean look, and it is a good idea to router the edge so it bevels in to create a nice smooth transition from the interior trim to the floor. Then finish off with padding, and whatever your going to use to cover it with. I have my floor set up so I can still finish it off with acrylic windows and back light it when I get back to it again. Like I said, work in progress.
Amyways, I hope that somewhat answers your questions, and as always, if you have any more, please feel free to ask away anytime.
Go easy, and I'll catch ya later.
Candyman