When buying a new filter how much do I need to pay attention to the recommendations on tank size? I figure as long as the filter isn't so strong that it provides too much water movement that it would be okay. Because turn over rate = good thing, right? Or could it be too much of a good thing?

Well, if you really overdo it you'll be paying more on your electric bill! Those of us with several tanks, expensive lights etc might already be paying noticeably more on the electric bill... if it's just the one tank it probably wouldn't make much difference there though.