Which CPU cooler to get?

Solution
That cooler should work. There aren't a whole lot of choices in a case that small. It should work better than the stock cooler (referring to the stock cooler that comes with a 6600 or 6500, obviously the 6600k doesn't come with a cooler). However if you're not planning to overclock (assuming from the tiny case and b150 board), you might consider the i5 6600 or 6500. The k version isn't any faster at stock than the non k, just a bit more expensive.
That cooler should work. There aren't a whole lot of choices in a case that small. It should work better than the stock cooler (referring to the stock cooler that comes with a 6600 or 6500, obviously the 6600k doesn't come with a cooler). However if you're not planning to overclock (assuming from the tiny case and b150 board), you might consider the i5 6600 or 6500. The k version isn't any faster at stock than the non k, just a bit more expensive.
 
Solution