I need to put all my ram subtimings to their highest settings, but that hardly does anything to performance (63-15-15-15)
Why do you need to do this?

I would think that this would horribly affect performance. Maybe not in all benchmarks, but in real-world settings it would. I'm assuming your CAS latency is 15, that is three times as slow as a setting of 5.

Am I correct? I'm just starting to learn about ram timings.