As Ian says, you've got a bunch of bad performing parts that can't work well together. You'd need to change at least 2 of the 3 to get decent performance. I'd change all 3.

1) 1/2-10 acme - Requires the motors to spin too fast, where they have little torque. Best case with 1/2-10 acme is usually 80-100ipm max.
2) The 425oz motors are very poor performing at higher speeds, unless you can provide a LOT of voltage to them, like 72V from a Gecko G201. According to Gecko's power supply formula for maximum performance, those motors need about 80V when wired bipolar parallel,, and 160V when wired bipolar series. Even a G540 will only give you half the performance the motors are capable of. I'd recommend new motors to go with the G540.
3 )From what I've read, those drives are cheap, but not very good, unless you have a small, slow machine.


Bottom line.

The G540 will help, but the combination of those motors and 1/2-10 screws will still result in about 100ipm speeds. Changing to 1/2-8 2 start might double that. Changing motors to these http://www.kelinginc.net/KL23H2100-35-4B.pdf might get you 300ipm, but you may reach a point where the screws start whipping, which would require switching to 1/2-10 5 start screws to slow the screw rpm down.

Your motors are also rather high inductance, which will affect speed.  Particularly with the G540, you might well be better with lower torque motors that have lower inductance, like one of the 2mH-ish 380 oz-in motors.  The ones you have would work best on a much higher supply voltage, which neither your current drivers, nor the G540 will drive to their best performance.

Regards,
Ray L.

These are my beefiest motors. I don't have motors any bigger than these.

This is a case where bigger isn't better. Most smaller Nema23 steppers will have more power at the higher rpm's you're looking for.

When wiring motors -
When do you wire parallel or serial? I just rewired for parallel instead of serial on my Y axis and I can change the velocity and acceleration a bit faster and not have it stall.

Thanks

To change everything to 5 start instead of single start seems to be the most expensive upgrade. I think I am going to start small and work my way up. Gecko 540 & Power supply first and then 5 start and then the motors? Or maybe motors and then 5 start.

Current plan -
Rewire for parallel instead of serial??

You can't - you don't have the amps

Future plan to increase speed
Gecko 540 and what voltage/amp power supply using the motors I am using??

These motors are not good - if you're going gecko and a new PS - do them justice - get "better motors".

These are my beefiest motors. I don't have motors any bigger than these.

In your OP here http://www.machsupport.com/forum/index.php/topic,16875.msg114422.html#msg114422 you have a picture of two motors - they are very different. The KL23H276-30-8B is the beafier one I was talking about. Totally different and much better spec.

When wiring motors -
When do you wire parallel or serial? I just rewired for parallel instead of serial on my Y axis and I can change the velocity and acceleration a bit faster and not have it stall.

See above - you don't have the amps for parallel

But to answer your question: Generally speaking serial gives more torque at lower speeds but it soon falls off with speed, parallel gives less torque at lower speeds but extends the torque into higher speeds.

Meanwhile with your current kit: You could try changing from serial to single coil - your specs are still not good but single coil should beat serial hands down.

Ian

Ian -
What is single coil?

Let's assume I have the money to do all three at once (which I don't it will take a while) -
If I got the Gecko 540 (I want to add a rotary axis so figure this would be a good choice being 4 axis). power supply and new motors. What volt/amp power supply should I get with what motors? I want something that will be good and fast. Just have to budget for it.

On my current driver board posted above -
What is "Decay Mode Setting"? Not sure what this means or how it effects things.

Thanks

All the advise you've received is really great. No mistake about that. But.....
I would have to echo what Rich stated in his first reply.

define the intended use of the machine
IE; - define the desired axis feedrate / IPM

That right there, is really the key part of information you should be concerning yourself with. If you define the desired speed, everybody can give you a more accurate detail of what you should do. If you don't really know what speed you want, tell us what your going to be cutting, and the people around here will know what speed will best suit your needs. "Speed" is a common pitfall of 99% of beginners. "Most torque at cutting speed" is what you should be after, not how fast you can zip around the table. If all your wanting is to go faster, my spidey senses tell me your going to be right back in the same boat your in now, with a whole lot less money, and a whole lot more aggravation....A machine that does not do what you desire.

I am using the machine to cut various woods for guitar bodies or sign making.

here is what I cut out last night
http://celticmachining.blogspot.com/2011/01/here-it-is.html

If you don't really know what speed you want, tell us what your going to be cutting, and the people around here will know what speed will best suit your needs.

I do not understand enough to state what speed I really want. How ever the sign in the link I gave measures approx 10 x 20 inches and it took a few hours to cut. I would like to keep the accuracy and quality I have up till now and maybe improve as I go but also speed it up to where that job might of taken an hour or hour and half instead of 3 - 4 hours.