Hello ofekfischer;

Should fit your Antec 300. It's 160mm tall and the 159mm tall CM Hyper 212+ is known to fit OK.

Already have the Scythe SCNJ-3100 120mm Ninja 3 Rev. B CPU cooler?
We can probably find an equally good CPU cooler for a bit less. Like CM Hyper 212+ Evo.