Admittedly, I purchased the PL2 without benefit of an audition. At the time, the price difference between the PL1 and PL2 was on the order of $200 or so and I figured that the upgrades were worth a relatively nominal sum.
I use EL 34's in both my PL2 and PL5. I tend to agree with your assessment of the KT88's, they add a certain ballsiness to the sound that I did not care for. I liked the sound of 6550's, but I was only getting a few hundred hours of use with them and I tried a variety of makers. I have been using Electro Harmnonix EL34 for the last few months ... a good compromise on sound and longevity.
Regards,
Rich