My initial build used the xPro V2 and I love the form factor and virtually everything about the all in one driver. But I did experience many of the trials of setup for getting the current setting right. With all the tweaking and micro stepping set, I still got rough movement when cutting hard material - had to slow the feed rate down which I think contributed to the problem. Decided to experiment with a Chinese TB6600 4 axis board and I know all the negative warnings, but I thought it would be worth a try. Got it in, set the current dip switches, and connected to an eBay old Dell computer running XP. Runs super smooth and required no tweaking. The board appears to be well made with good solder joints. For $50, it was worth a look. Will probably buy a spare, just in case. My first choice was the Gecko 540, just couldn't justify the price just to see if I needed more current. I have my TB6600 set for 3.2 amps on my NEMA 23s that are rated at 2.8. Any experience with the Chinese TB6600 boards? UPDATE: see below. Abandoned the TB660 4-axis board as one of the Y channels started acting up. Now using Gecko G540.