I used 12mm MDF, mounted some 6x9s and then carpeted the whole lot. Just looks like a factory shelf as i mounted the 6x9s on the underside of the MDF and carpeted right across the whole thing so it lies flat. It also stops thieves from thinking they're gonna nick your speakers if they can't even see 'em! You'll also be really surprised at the sound quality and volume just running them off your head unit. Sounds really good... for a while, but now I want more! So I'm looking into subs, etc. As for front door speakers, I uprated them and they really compliment the 6x9s with some higher range frequencies, just be carefull of the mounting depth. I think its around 60-70mm, quite shallow because of a support in the door. You can't mount speakers in the roof or rear cards because there's no mounting depth, so unless you're planning a big custom install just save your money. If you want it to look the dog's nuts then go for it, otherwise just stick with the shelf and door speakers. You can get speakers with tweeters mounted in the middle, thats what I've got.