Cut a few holes with a Dremmel 300, one at bottom, one thin one at top and little one on drive bays.
Get some edging trim, I got mine from Chilled PC http://www.chilledpc.co.uk/shop/product_info.php?cPath=...
Cut it at angles into the corners, you can just wedge it in in one piece but I think its a better fit when cut individually.
If it doesn't hold too well you can always add a little dot of glue, this stops the cables from rubbing.
Finished unit, yes only 1 GPU but you get the picture. Really helps with airflow also.
And a bit of arranging round the back.
As mentioned this isn't a groundbreaking setup but a massive improvement for a little work.
Only other thing I needed was an ATX 8 pin extension cable so I could run it behind the top fan and through the new hole.
Maybe you don't need that new case after all for a clean looking setup.
Hope this helps a few people to give it a go.
It has a few tie wrap clips and the section round the back for cables but the extra holes clear the cables from the base of the case and the front usb/power etc cables from the top. I can't believe how much better it is and pretty simple.