Speed is the thing that make one press better or worse than another. Most all forging presses have more than enough power to squish hot steel. 1" or less IPS is the goal.
The feature that sets a nice press apart from a super press is automation and hands free operation. Adding a controller, operated by a foot switch, will make the up/down cycles easier to do and allow both hands to hold and guide the billet tongs. Making that controller automated so it goes up and down ( somewhat like a slow speed power hammer) at a pre-set rate ( which can be adjusted) will make things like drawing out a billet really rapid and easy. These additions are not beyond the ability of a good tinkerer who understands hydraulics and electronics. It requires a solenoid valve and a timer controller that is activated with a foot switch. The great thing is that it can be switched from manual to automatic with on flip of a switch ... and the foot control will run it either way. Kevin Cashen posted a thread on his automated press a while back. The topic got a good discussion going. Eric Fleming build one that was nice. here is the threadhttp://www.bladeforums.com/forums/showthread.php/648250-WIP-Hydraulic-Press-Build .
If getting the press built for you, a hydraulics company should be able to make up the solenoid unit and an electronics friend should easily make the controller. It is not much more than a couple of adjustable time delay relays on octal sockets. The rest is a few switches and lights, plus a two pedal foot switch. EBay has all these for very little cost.
A mechanical method to control the press is similar to a power hammer foot ring. You make a "U" of steel that is hinged on the ends. A linkage goes from the foot bar to the valve handle. Step on the bar and the handle gets pulled down - bringing the ram down. Release the bar and the ram returns ( a spring is attached). This works well for a simple conversion press made from a log splitter.
As far as stroke, all you will likely ever use is a couple inches. Most strokes will have only about a tenth to a quarter inch of active pressing. The time to get to the surface is wasted time. This is why two-stage is used. If the press is built with an adjustable anvil height, then the ram travel can be kept to an inch or less. This allows use of a single stage pump. The travel adjustment is as simple as stacking a pile of 1" thick steel plates on the base anvil. A 6" to 8" travel ram stroke is more than sufficient.
Ram diameter is how you get power. The bigger the ram cylinder diameter, the more power. Also, the bigger the ram diameter, the wider a billet you can work efficiently. You must stay pretty much in the center of force area to work the steel. Efficiency drops rapidly as you go out of that zone. Get too far out and you can bend the ram.
The bigger the cylinder diameter, the more oil it will need to move it. This requires a bigger pump that delivers more GPM. 6GPM is a normal minimum, and 16GPM will give you a lot more speed. Normally, the pump size and motor to drive it will determine what size ram you use. You also need a sufficiently large oil supply to feed the pump and ram. Having enough oil also helps keep things cooler. Obviously, good filtration and a tank magnet for any steel dust or shavings is a must.
You can't power a forging press with a little motor. If you try, you will trade either power or speed for the low current use. Yes, there are 30 ton presses at HF that run of 5 amps 110VAC. They also take 30 seconds to move an inch. The math shows that the amount of power needed to get the desired speed and power is usually between 3HP and 5HP for an electric motor. If using a gas motor, double that. This means the press will need a large power supply, or an outdoor location.
