I'm in the UK.
Been just a bit busy with a nightmare grinding job, which isn't going quite to plan.
If I were you I would try to keep the original motors if they still work ok. You may even be able to keep the orginal drives, although they would probably be lower performance than a Gecko. The critical thing is to find out if your drives are compatable.
Modern drives like the Gecko are microstepping drives, which gives you much smoother motion than the older full and half step drives.
Other items on your machine you may be able to keep are the power supplies, if they are suitable for the Geckos (if you go that route)
I did look at the Automation direct drives you mentioned. They were not only more expensive than Gecko's but also only 35v 3amp if I recall correctly.
The voltage is really what determines your motors speed and the current the torque availble, thats a very simple explaination! If you motors are 8amp you should attempt to run them close to that.
On my stepper system I run my drives at 72v, and my motors are 4.5amp. It works very well.
Wayne....