I have the same player, for about 3 years now, and have similar experiences - sound quality is just very good, and tube rolling will make a clear difference, at least for the output tube. I liked (Dutch) Amperex 7308 very much, and also NOS TESLA e88cc (goldpins and not JJ) sounded clearly better than the stock (philips) tube. The TESLA's gave me a slightly rounded low-end, but great, lucid highs. The 7308 have slightly more edge, but also go deeper, maybe less tube-like. Choosing between these two was merely a matter of taste rather than sound quality, however.
And even with the stock tubes, it sounds better than my tubed Marantz Heart 6000 (and check those reviews on the web!), deeper lows and sweeter highs, and HDCD! It may be a dying format, but cd's that do have it, show a better soundstage, so it's well worth it!
Only problem I had with was strange hickups in its sound. I was going to send it for repair, but I swapped the power supply tube -more or less for unclear reasons- and my problem was solved
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