Hi,
I strongly support what Roger proposes. By far and away the weakest link you have is the drivers. Replace those with good ones you may well find everything else
is good enough, and no matter what motors or powersupply you use is ever going to make up for poor drivers.
I use Vexta 5 phase steppers, 5 phase is somewhat esoteric but they have a few advantages. When I first got them I used a homemade, home design driver, quick and nasty. I was
somewhat disappointed at the motors particularly as I paid a real PREMIUM to get good quality. Eventually I bought the genuine Vexta Drivers that are specifically intended for these motors,
they have an open circuit voltage of 150V!. They are absolutely superb, they spin my motors at 2400rpm all day and have not missed a step in four years. Without those drivers the motors
are really very average.
Craig