Actually scratch that - it's the way I work it with folder view (file name), but for the tagged track numbers I combine both albums and number accordingly. EG for 2 albums of 13 tracks, I number from 01 to 26.
Covers both bases.
X1 by itself with HD600. Listening to Alison Krauss & Union Station's "Paper Airplane" album - which is decently recorded without being overly compressed. To deliver an average SPL of 75-80dB (which for me is actually slightly louder than I'd normally listen), is taking approx 60/100 on the volume dial of the X1. So it should handle the HD558 OK. You may struggle with really dynamic classical - but for most music, it should handle OK.
Altone - more quantity bass, can appear slightly clearer (but isn't), more euphonic upper mids (female vocals), but still has that dip in the lower mids. A83 - better quality bass, but still there, and still has good impact. Much better balance, and cohesion between upper and lower mids. Much, much better build. Great for listening at lower volumes.
Would pay to also mention what you're expecting from such an upgrade.
If you're looking for clarity - but better balance, and better bass quality - along with much better build - then the Fidue A83 would be my recommendation. I've reviewed both.
It can drive the HD600 (300 ohm) and DT880 (250 ohm) perfectly fine for my tastes. Are they at full potential - I think that's a subjective call. Are they good enough for me to listen to without needing an additional amp?
Yes - emphatically !
It can also drive the T1 (600 ohm) to a pretty loud level, but they are a little brighter than on my desktop set-up. Could be the DAC. Could be the amp stage. Could be that they need more voltage. Are they good enough to...
For solid state - the Audio GD-NFB-15 (dual Wolfson WM8741) has nice full sound with a little warmth. Pairs nicely with the HD600. For an OTL Tube - I can recommend the Little Dot MKIV as a reasonably priced tube amp with plenty of rolling options.
I'm pretty sure that what you think is the protector is in reality the cover for the protector. It comes in two pieces - the protector itself, and then a top plastic cover that should peel off with the paper tab. it worked perfectly on mine. I think maybe you're trying to leave the cover in place, and it should be removed. Trying to remove the tab from the cover is difficult because it's not meant to be removed from it.