Just to see what else is out there, anyone wanna post a few pictures of their 300g+ tanks? Maybe give me some ideas? Or just show them off to everyone? Lol
In case the OP revisits this project, I would definitely not use the pump you originally planned to use. That thing draws 750 watts!...it will eat you alive on your electric bill. Get a Reeflo Super Dart Gold. I'm running one on my tank and it only draws only 175 watts and pushes around 2,200GPH at 9' of head pressure.
Also, getting an ettore Grip N Grab is a must for a tank this deep.
And lastly, you can build your own monster sized gravel vac. Here's mine in action: