I have a 550d which is a similarish to your case which I am watercooling but you are looking for more rad space than I was. I put a 240mm monsta rad that is 80mm thick up front where the drive bay goes to cool my 2500k and 7970. I also used the corsair SP fans. When I turn all the fans down my rig is very very quiet, near silent, and my 7970 reaches a high of 50c while overclocked. I usually keep the fans a bit higher just because I like better temps and the noise is not that bothersome.
http://i.imgur.com/BBtCSPU.jpg
That is just my rig. I am showing you this just to give you ideas. You can do whatever you want. I just love my apogee drive II and would recommend it to anyone because it saves space and works awesome. You are probably going to need at least a 240 if you are just doing your gpu's but anything more than that just means you can go quieter. You need to do is figure out how much you want to spend, space you want to use, and how much cooling and quietness you want. Be creative and figure out where you can fit your rad and how your tubing will run. I really recommend getting some good fans because that will be how you make your rig quiet. You could get some low rpm yate loons like manofthem which are near silent. It might be a good idea to get faster fans and have a fan controller to turn them down to a sound level you find acceptable. I feel like I am just throwing out information, but that is because I am just trying to give general information since you did not ask for specifics.
Some good shops are performancepcs, frozencpu, sidewiders, and jabtech.