Take a look at the pic below and note 2 things:-
(pic source: http://hardforum.com/showthread.php?t=1653246)
1. it is not possible to fit a 360 radiator on the bottom, not because of the rad thickness but the length is too long unless somehow you remove the PSU to some place else.
To fit a 360, one option is to do it outside of the case to the rear.
2. it is possible to fit a 240 rad to the bottom. The length of the graphics card(s) basically dictates the combined thickness of the rad + push fan + pull fan.
For visual comparison:
-On the left, the fan is the stock 180mm AP fan which is 32mm thick.
-On the right, total thickness is 32mm (FM181 fan) + 32mm (180mm rad) + 32mm (180mm AP fan) = 96mm. Obviously this has conflict with the lengthy Asus HD6970 DirectCU II (with 297mm length).
However, as the Koolance HX-CU720VS is just 38mm thick, making a total thickness of 32+38+32=102mm, I suppose this rad would fit as your GTX570 measures only 267mm (30mm shorter than the HD6970DCII).