pond pump choices

[scoot15738]

Hello, so my 9 year old pump is starting to lose its power, and is just not pumping water all that well anymore, my pond is probably about 450-500 gallons and i looked it up and found out its only a 300gph pump, and i was looking at this pump, on ebay, 700gph pondmaster for 75$ or these other 2 on drfosters 570gph and 640gph, i think i might go with the 640gph, they are both mag drive. which would you all suggest, im redesigning the waterfall so it has a couple tiers to it with a makeshift stream with river rock in it, nothing too big but i dunno if i will have too much water running through it or not enough. i always thought more was better, but too much might be bad too. Thanks

 

[DrCase]

Its never too much water
you can always divert any excess water some were else

 

[scoot15738]

im going with the smallest 640gph, which would be over twice the water of the current pump im using....plenty