My 940 was CNC from the factory, with 640oz-in in the X and Y, and 1200 in the Z. I would STRONGLY suggest 1200oz-in for the X and Y, and at least a 1700oz-in for the Z... However if I were starting from scratch like you I would go with a Nema 42 for the Z with 2800+ oz-in. You're not going to wake up one morning and say "damn I wish I would have used smaller motors" but I wake up all the time thinking about upgrading.
Budgets are budgets though.
Also, I would suggest direct drive. It works great, is simple, and less room for error.
PZ