powerhead question

I'm going to petco later tonight. And I wanna know what size powerhead will work good for a 55 gallon tank. Right now I have one that is a 950 says it's good up to 55 gallons but it doesn't give off alot of flow so gonna get one at petco tonight depending on what they have but what size or volts is a good fit? Plan to put it on th other side of my tank. So they both get good flow at both ends