The only problem that you will have is noise. The fans will run at full speed; this generates noise. The idea of the motherboard fan ports is to allow the fans to run more slowly, thus quietly, when the components they are cooling are not hot.
1 More question. If I buy Corsair fan quiet edition which comes with voltage step-down adapter for lower speed operation will it still run at full speed which is 1650RPM or it will run at 1100RPM as listed on Corsair's website?
Fan is: Air Series AF120 Quiet Edition High Airflow 120mm Fan Twin Pack