I think I'm going to have to upgrade the pump I have now. On the highest setting, I don't get much pressure coming past the check valve. Water flows alright, but not at a fast enough pace. And with only 1/2" plumbing, this isn't a good sign.

I'm looking at something over 1000GPU, and a max head of about 13-15'

1376 GPH Pump Water Fountain Pond aquarium Submersible - eBay (item 180329093938 end time Mar-17-09 06:43:11 PDT)

They also have sump pumps for a reasonable price, 1/2HP that pump much over 1000GPU, but i'm sure use much more power.

New 1/2 HP Submersible Dirty Clean Water Pump Pond Pool - eBay (item 260375027588 end time Mar-14-09 18:44:57 PDT)