great project, there is no "enough" with "power", especially with lasers!
some points, though:
-if you and everyone else has to wear eyeprotection, which is obviously an undiscussable fact, you wont see that much of the beam neither. it will look like, say, 100mw or 10mw, and be as impressive as that too. well, like a 10mw beam which burns all stuff it is shone on!
-a reflection would *still* be potentially blinding/deadly, even with eyeprotection. just too much power, even for shades. if you get shades which protect from a direct hit, you will either not see anything through it, or pay more than for the actual laser. which would be a good thing to do nevertheless!
-six laserdiodes.. combination is *difficult*, despite its been done and everyone would like to do it. not sure if i understood you right, but if you plan to use combining cubes *only* to combine more than 2 diodes, it will simply not work at all. no "work badly", but "work not". there are many threads about combining more diodes, it *is* possible, but not easy, and portability has its own difficulties as well.
-use TEC-cooling, pretty please! i bet you know the "open can with TEC" thread! ;-)
-i just forgot another point i had to mention.. wait..
-oh, right, the ps3 drive has a nice polarising combiner cube, 5mm sounds right. since there are so many drives bought here by people, start a thread to collect some of them?
sorry for that much critic and slowing sown.. i *definitely* want to see you do it, and will help with more-or-less helpful hints whereever i can! do it, and do history!
manuel