The only concerns I would have are:
1. The TB6600 is rated at 4.5 amps continuous, 5 amps PEAK. That means 5 amps for very short periods of time. Saying that it can run continuously at 5 amps is deception. It's still much better than the TB6560's though. The TB6600 might actually do 4 amps continuous and the TB6560 can't do 3 amps for more than a few minutes without burning up. I'm not sure then can do 2 amps. Totaly piles of crap, they are.
2. It's nice to buy an assembled and tested unit, but if you didn't build it, it's harder to repair it. So be very careful. I like kits. Yes, you have to solder them together, but then you know how to fix them if anything goes wrong. And yes, I'm biased, because I sell kits. ,o)
3. We assume you mean NEMA 23 motors?
James hosts the single best wiki page about steppers for CNC hobbyists on the net:
http://www.piclist.com/techref/io/steppers.htm Disagree? Tell him what's missing! ,o)