My XA60.8s should sound pretty similar to your XA30.8, but of course this still leaves some variables:
- our tastes
- our rooms
- our other equipment (though I do have a Bartok)
I did a few similar comparisons recently, and while I didn’t try any tube preamps the experience might still be of interest to you.
I loved the sound of my system using another Pass Labs preamp — the XP-30. The HPA-1 was good, too, but nowhere near as good as the XP-30. The XP-30 could do warm and lovely with the best of them, and it almost never felt I was missing out on the detail and the delicacy I got going direct. (The XP-30 comes up reasonably regularly second hand, and for obvious reasons works amazingly with other Pass gear.)
If I had the Bartok set to output 6V I preferred the sound with the XP-30 to going direct. At any other setting, though (e.g. same preamp, but the Bartok at 2V), I preferred the sound direct. I did this at 0.6V so that I was using attenuating as little as possible with the Bartok.
It was lucky I even tried the preamp it in this configuration, actually — I was ready to sell the XP-30 and upgrade the Bartok to a Rossini or a Vivaldi, but some helpful people on this forum suggested I try at 6V first. (Helpful? Or a menace? 
)
Your English is great — no excuses needed!