Periodic Stalling of X and Y

I hope to sort out my festering problem with stalling motors. I made this video to help describe what I have going on, and if I in fact have a "problem" or if my machine is just at the peak of its ability. Nuts and bolts of it:
X and Y motors are KL23H2100-50-4B
Z Motor is KL34H295-43-8A (Wired Bipolar Parallel)

X/Y Driver is KL5056D
Z Driver is KL8070D

Both drivers set for 1/8 microstep, Half Dynamic standstill.
X/Y motors are rated at 5A and my drivers are set for 4.9A
Z motor is rated for 6.1A and my driver is set for 6.1A

Motor Tuning (setup in mm/min):
X and Y are at 1800 Velocity and 400 Accel
Z is 2000 Velocity and 400 Accel

If I move my X/Y up to anything over 1800 I get periodic stalling. If I go all the way to 2600 it is guaranteed to stall in rapid moves 80% of the time. Never had Z stall out.

So is this just the limit of the system I have put together? It is not the end of the world as I don't cut anything at the moment above 1000mm/min but I would like to know for my own satisfaction that I dont have something wrong. Some systems advertise advertise 300 to 1000ipm rapids, that's 7620 to 25400mm/min!!!! WOW I am way off that number.