do i

they do help with water movement. tell us more about your setup and we can give better answers.

never hurts to have one blowing at the top for gas exchange...

That really isn't a lot of watermovement for 125g tank. A powerhead or two would make a world of difference.

i would look at getting the hydor koralia model or a powerhead like them. they have good water flow but distribute it through a good area versus being direct. They work well for me, and you should really increase the turnover. I like the 10-12 times but IMO i would shoot for higher then at least 7-8 times turnover per hour.