Belated, but I played through KQ6 (Amiga version) with the Companion as my guide and did perfectly fine! Only thing is of course that the Amiga version was altered a bit for space constraints, so I had to use my initiative a bit in terms of figuring out WHAT was removed, but the guide was brill! Also using the original instruction manual to solve the Cliffs of Logic was absolutely mind-blowing.
I will second any recommendation to get the GOG sets of the KQ games (they seem to go on sale quite a bit, but I paid full price for all three sets and it was worth it), although I would perhaps recommend emulating them through SCUMM instead. With regards to KQ6, that'll give you the hi-res character portraits with the CD voices, and in terms of the earlier games, you can choose a different sound set if you don't want to listen to the bleepy noise versions.