Servos', what type, what torque?

Hi all,
I have a Chevilier turret mill which I intend converting to cnc using
EMC. I have no experience with cnc, but I have been convinced that I
should use servo motors for smoothness of opperation i.e. no stair
stepping in gentle curves and tapers etc. I've been checking out a
few sites and there's reference to a/c, d/c, brushless motors etc,
and I'm a little confused about what type I should be going for. The
torque level is also an issue which I'm not sure about, the machine
is fairly large, the table is 50" by 10", much the same as a
Bridgeport. I will be using x,y,z and at a later stage a rotary
table. Any suggestions of what specification motors I should use or
discussion of the pros and cons of the different types would be
appreciated.
Thanks
David Preston