Pointless making a comparison with Pentax lenses since they will not fit an M8. If they are are as good as Leica lenses, they've certainly come on some way since the last Pentax lens I used.
If you want 3 good quality lenses, I'd recommend the following:
- Summicron-M 1:2/35 - this is the last of the different 35/2 generations before the ASPH version, you will see it referred to as the Summicron IV. Just lovely. - Summicron-M 1:2/50 - if you get a recent lens, it's one of the best non-ASPH lenses Leica makes. - Elmarit-M 1:2.8/90 - lovely compact telephoto with built in hood.
All three are codeable, ready for your move to the fabulous Leica M8 in due course.