Questions before buying

I want to do 3D carving with a cnc from 3D files generated with Artcam. Is Xcarve the right tool? as in the spec the Z axis is set for 8.6cm, but in the FAQ we have wood+bit<6.7cm. So with an average bit length (after the collet) of 2cm, the remaining is between 4 and 5 cm. Not a lot. Could the community help me to compare with the chinacnczone 6090 that is at the same price than the 1x1m but with a z axis of 15cm and a 4th axis? Is there a way to add a 4th axis to Xcarve.
Thank you for your comments.