Out of those 3 I'd suggest the 50z....it's not about the GPH or even necessarily the voltage. What you gotta look at is the head, which means how high the pump could push water straight into the air assuming there is no restriction in the flow like a water block. At 0GPH that hydor pump only has 7 feet of head which is pathetic. The 50z has I believe around 11 feet of head at 0GPH.
All in all I'd go with 50z or the D4 pump also known as Swiftech MCP650. A lot of people at xtreme says the 50z is better and quieter, but I Have a friend with the D4 and a couple people have had problems with the 50z dying quickly, but of course I suppose you can have troubles with no matter what you buy.
Either way I'd say either 50z or D4....I just ordered a D4 for myself last night
Thas right gaara you heard it!
Got the TDX + D4 combo at dangerden, they had it for a special price as a combo deal.
Got a brass top conversion for the TDX and the accelerator nozzles set which after buying those makes the combo only like $10 cheaper than buying the TDX with brass top and nozzle set and D4 pump seperate, but hey, $10 is $10
Won't be for another couple of weeks that I can get the rest of the stuff though, weaponcore and MAZE4