The encoder resolution on the servos can make a big difference in how much speed you can get from 23,000 KHZ. I purchased a servo system on eBay and the decision not to ask for G340's was that it had a 250CPR encoder (1000 quadrature).
1000 quadrature @ 23,000 = 69 IPM
1200 quandrture @ 23,000 = 57.5 IPM
1600 quadrature @ 23,000 = 43.125 IPM
2000 quadrature @ 23,000 = 34.5 IPM
I thought 60 was more than enough and if it turns out I can run at 35,000 or 45,000 KHZ I will have all the speed this mills 20 TPI screws can handle. BTW total system cost (which is well put together) was $1050 + $30s/h and his ad on eBay suggests he has more to sell. The servos are listed as 360oz and impress me just on the bench having not used them yet.
http://cgi.ebay.com/CNC-router-contr...QQcmdZViewItem
According to the AD this seller makes custom systems for resale maybe you can get something like this or better for your TAIG. I'm sure some will say 360oz is too much but even if its more than "needed" I will have something for when/if I can use a bigger machine.