I'm guessing it'd have slightly worse airflow, but on par or better than a generic case. Only one front fan and one exhaust fan could work, but more is better, no?
PSU wise, on paper it's better than Antec's old PP303X (that shipped with the old SX830 and SX1030). I thought the PP303X was a good PSU so the SL300 should be more than good enough as a 300W PSU. If a 300W fits your budget setup, I think it'd work fine.