What should I upgrade first amp or preamp?


I need your help. I have OPPO BDP-105 connected to PASS Labs XP-10 and XA-30.5 driving 89 dB at 4 Ohm Snell C7. Looking to upgrade my system and planning to spend $ 3000-4000. I live in the apartment building and unfortunately can't listen to music very loud (no more than 58-62 on the XP-10 display).
What would you suggest to do, upgrade preamp to XP-20 first or amp to two XA-60.5 or to XA-100.5 and why. Upgrading an amp is more problematic due to the space constrains.
What will I gain and what should be the difference in sound in each of those cases?
Thank you.
karapuz
Forgot to say, my speakers are tri-wired, so truly speaking I have wires that 3 times thicker than regular 12 gauge cable wires. Do you think I need something different?
That all sounds good to me, assuming that the Analysis Plus interconnects are the XLR versions. Frankly, I don't see anything that particularly stands out as a weak link, although I have little familiarity with the XP-10 preamp.

Regards,
-- Al
I know you aren't a big fan of tubes but if you were to throw a Herron VTSP-3a in there, the sound wouldn't go tube-ey. You'd just get a better sense of space and timbre without sacrificing any dynamics. I've been a high end passive guy forever and even tried some SS preamps but it wasn't until I tried a very good tube preamp that I finally got the sound I was looking for.
Of course, they are XLR's. What's the point to have fully balanced equipment without using XLR interconnects.