Thanks for the comments so far. I should have provided more info.
The spindle motor is a servo motor WITH and encoder and is driven by a servo drive, so although I agree with the assessment given relative to PWM vs SCR speed controllers, it does not apply in this case.
The servo drive will limit the amps to whatever I set it at up to 35amp max. The drive is rated to 160V.
Confusion sets in, methinks, when I apply stepper motor thinking to servo motors. If one considers the voltage rating on a stepper vs where they actually run, there is no correlation. My experience with servo motors so far shows me that a servo motor can run much higher voltage than it's rated voltage on an axis where it has plenty of rest time, but a spindle motor has a different environment and my concern is overheating. I can cool the spindle relatively easily, but I have no practical method of cooling a servo motor. It is my understanding that amperage causes demagnetization, not voltage, although I really don't understand that whole phenomena.
Ironically, the idea of running rectifiers in series for double voltage comes from Antek themselves. I should clarify that this is only applicable to a pair of rectifiers running off the same toroidal coil, as is the case with my current PS and the 1,500W models from Antek.
What I am after is to get the full RPM's from the motor that I was expecting. the belt ratios on my new mill were designed around Keling's specs, which I now suspect were exaggerated. The motor does not run at the spec speed, even after deducting 20% as indicated by several tech articles on the subject. I can easily get the speed back with higher voltage and I am going to purchase a separate PS just for the spindle, so that is the basis for the question here. My alternatives are grim; buy another motor or redesign my carefully chosen ratios on my two speed mill head. I sold my old mill and my two Minarik PWM drives went with it, so as a diagnostic I have purchased another Minaric cheap off eBay to run the spindle motor on 130V 5A to see what speed I get and if the motor gets hot.