300 is enough as that's what I ran a similar setup but with more HDD's on a 350W. However that case has a SFX power supply which usually suck.
Instead of getting what you posted in the OP I recommend something like this:
NCIX.com - Buy Silverstone Sugo SG01B0-F Evolution Black SFF mATX Case 2X5.25 2X3.5INT No PS - Silverstone Technology - SG01B-F - in Canada
Here's another that's cheaper:
http://www.ncix.com/products/?sku=28...e%20Technology
and slapping a nice PS into it.
I'm using the same one but in aluminum plus it'll accept a full size atx power supply vs the crappy sfx ones.