I crew a 1985 Catalina 30 out of Ventura that I found for my buddy as a live a board. We take "His house" sailing!
For us, seeing 6 plus on the knot meter is normal going to wind. I back these readings with my GPS. We have seen the knot meter hit 7.4 sliding down a wave on a broad reach. The admirable, my wife, has a squeal meter that goes off at 15 degrees so I ease off the main and run the traveler down hill.
Bottom line is that any forward speed is good and being able to trim for "no hands sailing" is the best. We aim for comfort sailing.