So I've got a Gigabyte MB GA-X58A-UD3R which supports both voltage and PWM control for the CPU fan. The PWM fan with the best CFM/dBA ratio I can find at my local shop is the Noiseblocker M12-P, with a ratio of about 3. For almost half the price I can get a Silenx IXP-74-14 with a ratio of over 5. I see lots of glowing posts about PWM on here, but why wouldn't I save money and get more airflow for less noise?