What should I upgrade first amp or preamp?

Thank you for your responds. I looked at ModWrite ipgrades befoere, however I'm not a big fan of tubes and prefer SS in all chains.

So, do you guys really think that both preamp and amp are good and sufficient enough and don't need to be changed at all? Regarding cables, I have 10" Analysis Plus Black Oval 12 speaker cables as well as 1.5 m Analysis Plus Solo Crystal interconnects. How good are they in your opinion?

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?

Of course, they are XLR's. What's the point to have fully balanced equipment without using XLR interconnects.

Thank you all for the answers. I really appreciate your help and advices. However, I still can't decide what to do. It's so difficult, especially if there are so many choices. Yes, XA-100.5 is much more expensive than 30.5 and I'll need to spend twice as much. At the same time almost everybody are saying that stepping up from 30.5 to 60.5 in my situation doesn't really make sense because differences are not going to be huge and step up should be to 100.5 to hear the real difference in details, soundstage, etc.
Should I change the preamp to XP-20? Will I see a huge difference? I don't know.
With OPPO I like its capability to play DSD from my hard drive and DAC in it is pretty good.
I'm not changing speaker wires and interconnects, as well as my speakers, I think they are also good.
So what should I do!!!??? :) Any other suggestions would be appreciated.
i guess, first I'll get the SPL meter and check the loudness of my system at the sweet spot and continue from there.
Thank you again.

OK, I measured the volume of my usual listenings and got the following numbers: I sit about 6-7 ft from my speakers, average volume is 75-80 dB with 80-90 dB in peaks, max average volume (never got louder yet, but may try this weekend) is 80-85 dB with 95-101 dB in peaks. Most of the time the meter stays around 12 or moves for a second to 1 pm during peaks. Never stays over 12 for more than two sec.
Please help me to understand those numbers, how good (or bad) and efficient my system is and whether my amp is sufficient enough or I need to move up to the next level.
Thank you.