How often is it that a consumer machine becomes a professional machine ? Not often - although at Sony, it did happen more than elsewhere.
The PCM-2500 is the professional version of the DTC-1000ES. The 2500 is in fact made of two boxes: the drive+a/d/d/a & sync/AES section - 17kg in toto.
The 2500A could be tweaked to function on its own as it still sported the analog plugs inherited from the DTC-1000ES ; it retained the same build-quality as well: copper-plated chassis, select parts, a huge external transformer with many windings etc, etc.
Like on the 1000ES original, ABS Time was not yet implemented but one could indeed record at 44.1 from the analog inputs (by way of the 2500B and unlike on the 1000ES).
Many who have used the 2500 (or its original 1000ES) do regret having swapped it for a "newer" and "better" deck for these were built amazingly well, with an extremely reliable mechanism.
Sound-wise, the DTC-2000ES for instance smokes the 2500B, sure, but there was something more to these "older" decks, a little brilliance and generosity which made later decks seem a little too... polite.