Yes, 800 x 600 is a good resolution. We should take into account that a complete scan of an object sometimes needs circa 20-50 single scans. So after alignment the complete 3D file can easily grow up to values which are over the limit of our computer's possibility. Best is to use a 64 Bit operating system with sufficient memory (8 GByte RAM).
Fortunately, in the meantime, DAVID has become a 64 Bit software.
A tip for a cheap and simple "motor scanner":viewtopic.php?p=2016#p2016
In general it's better to sweep the laser line 1x very slowly over the object than multiple times very fast.