I don't think the V6 or V6GT would fit in a 300 it's only 8.1" wide.
I have a buddy with a CM690II which is 8.4" wide and the V6GT just fits.
The V6's in either form are 165mm tall, taller then most coolers which are 155-160mm.
As already mentioned the 212+ is a great cooler for@$30.
The V8 is an average cooler and was overpriced when first released.
And i think the Corsair A70 is a very good cooler for @$50 beats the V8 cost the same and comes with two fans.
The A70 is pretty close to the V6GT performance wise and cost $20 less.http://www.legitreviews.com/article/1389/6/