Without knowing the details of your system, it is impossible to predict whether you can get more speed with a controller update. You will likely get better smoothness since modern drives does microstepping.
Take a look at Geckodrive. As far as I know, any other quality drive that can handle your motors will not cost any less. Your mots are too big for the small drives.
You will need 3 of them, an 80v power supply, limit switches, case and lots of wires. A breakout board is used to connect your PC's parallel port to the drives.
You will also need software. Mach might be a good choice. I think it has a chaotic user interface, but it works well.