I don't see it having worse temps than the mess of a case you originally picked that cost more.
And the one I picked has proper support for a 240mm AiO if you decide you want to upgrade to one in the future.
I forgot that the p300 only comes with one fan, and you aren't using an AiO, so you'll need to buy additional 120mm fans.
2 for the front and one for the top for maximum airflow.
Here is the exact fan that the case comes with.
Should buy at least 1 so you can mount it along with the one in the case together at the front for intake.
Buying the additional two can be done whenever you have the funds.
Amazon.com: Phanteks Black Frame/Black Blades 120mm, Case & Radiator Fan-Retail Cooling PH-F120SP_BBK: Computers & Accessories
www.amazon.com