Usually fir balance of intake and exhaust, 2 and 2 is better. But you must look at the air flow pattern inside your case - well, try to imagine it. Is that likely to provide smooth air paths through the case, or would id creat odd tortured paths? It depends on what objects are where.
Another thought is this. Just a fan count won't tell you exactly what the balance is. I prefer to have slightly more intake capacity than exhaust, so the interior of the case is just SLIGHTLY higher pressure than the room. Why? For dust control. That way wherever there are small leaks of air in your case - around removable panels, at CD disk trays, etc. - air will leak OUT and not suck in plain room air. In the meanitme, you should ALWAYS ensure that your INTAKE fans have dust filters on their intake side to prevent entry of dust with the room air, AND you need to check and clean those filters from time to time. But those filters represent a small impediment to air flow, so the intake fans actually will deliver slightly LESS air flow than you expect for whatever speed they are at. Now, you can cimply ignore this issue. Or, you can connect intake and exhaust fans to different headers and alter the fan "curve" on the intakes to run a little faster than the exhausts for all the temperature settings. Or, you can ensure you have an ODD number of fans and use one more intake than exchaust. Or, you can arrange to have ONE of your intake fans a bit larger so it blows more air for the same speed as all the others. etc. For example, in your case, you could get ONE more intake fan for the front; you could even consider mounting both of those intakes at the front instead of one on the top.