First of all, don't modify your case for a 200mm rad. It will look terrible, unless very well done, and isn't worth it in the slightest. Stick to 120mm and 140mm based rads :)
Secondly, an i5 3570k is a great CPU. It is about the same as a 3820 in terms of performance, but the X79 chipset is much more powerful. If you need more than 32GB of memory (if you don't know if you do, or why you would, then you don't need it), or plan on getting more than one 670 FTW later on, then the 3820/X79 is the way to go.
Moving on, for the CPU block, I would grab a Koolance 380i. Best 1155/2011 block out there, right now. Looks great, and performs fantastically. However, most blocks perform within a few degrees of each other. If the 380i isn't worth $74 to you, then get what is :|
I assume by thin 360mm rad, you mean a physically "short" radiator with high FPI (fins per inch.) 360mm is a good size; fits in a lot of cases, and are great performers. I'm guessing you're grabbing either an EK XT or XSPC EX 360mm; both are relatively thin, and are pretty common. Not a bad buy, but I'm a fan of Aplhacool rads. For the thick 240mm, I'm assuming a "fat"(er) rad, with possibly lower FPI, but enough thermal mass to not require fans, necessarily. I recommend Alphacool NexXos Monsta rads; they come in all sizes (120mm and 140mm based), and are relatively cheap for what you're getting. Black Ice is another great brand for rads; don't limit yourself to what I'm saying. I like to stay away from 120mm rads, thick or thin; they just look wrong and ugly in a loop :|
Tubingdoes affect flow, but in a simple loop like yours, it doesn't really matter. I like to use 1/2" ID (inner diameter) by 5/8" OD (outer diameter) tubing; it is one of the largest standard tubing sizes out there, and has a rather thin wall for less kinking. I recommend Primochill Advanced LRT crystal clear tubing - great stuff.
Basically, to recap, if you plan on upgrading to more than 32GB of RAM, or multiple 670s, get a 3820, or even a 3930k, along with a socket 2011/X79 board. Otherwise, stick with the 3570k. Whatever you do, don't upgrade from a 3570k to 3770k; pretty useless upgrade, unless you can get the 3770k at a Microcenter ;)
Hope I helped :)