IMHO you are at EXACTLY the correct point to transplant into the final home.
There are 2 reasons for this:
-Stretch is virtually complete in the middle of week 2 and you will know how big your plants are ultimately going to get by then, and be able to choose the right sized pot
-Optimal residence time in any given pot of soil is about 6 weeks before potting-up, to avoid both soil stagnation due to excessive pot size and sections of the soil where roots haven't grown, or pH imablance due to soil salting from ferts or the lime being used up, which usually takes ~ 6-10 weeks depending on a few factors, so I assume 6 weeks to be safe. Transplanting 6 weeks from the end of flower is not a bad idea.

Don't worry abotu stressing the plant; it will be beneficial to give it a larger home with fresher soil. Just be careful not to mangle the root ball. Let the soil dry out pretty well, smack the bottom of the pot with your palm, and it should slide out with no hassles.