I agree in personal experence I have found maxijets to have good flow even at a few feet of head. Rio powerheads appear to not perform very well at a few feet head. At least the Rio 800 and 600's I have tried.
A maxijet 1200 should drain a 5 gal
bucket in about a minute if not a little longer.
TO use it to drain the tank just put the PH a few inches below the water suface in the tank. Put the drain hose in a bucket or if you have one long enough run it to a drain. Then plug the PH in and watch it pump out the water.
When your done dont just unplug it but also remove the PH as once the syphon has started it wont stop till the water level in the tank is below the PH.
A search at www.petwarehouse.com
turned up a maxijet 1200 for $20.99 before shipping. So its not very costly either.