I had the opportunity to audition the BCD-1 and the X-05 as a direct A/B comparison into a BP26/28B combination and both CD players were using identical cables. The BCD-1 is by no means a slouch, in fact it is a great performer. What you must examine again is the question of diminishing returns. I do not think it is fair to directly compare the two CD players as the X-05 is very close to two and a half times the price (approximately $7K CDN) of the BCD-1.
The first thing that I noticed before the play button was pushed, is the difference in the CD transports. You notice when the BCD-1 opens up its transport and you can really hear it. When the X-05 opens its transport, it is extremely fluid and makes very little noise at all. The X-05 transport (VRDS) with disc clamping is built to the nth degree.
As for the audio, I enjoyed the X-05 over the BCD-1. Was it a night and day difference? No, but you can easily hear the difference between the two CD players. An added bonus was the SACD, but I did not realize it at the time. I have never regretted purchasing the Esoteric X-05, it truly is an awesome CD player.
Be well...