Where I live the market is very limited, so no niche products like Calypso here!!
Interestingly Simaudio emailed me this about the W5 and W5.3
"P-5 and W-5 was the top of the line, a few years ago.
If we can compare P-5 and P-5.3 (sonically speaking) we cannot compare W-5 and W-5.3. The W-3 will be more as the W-5.3. The W-5 is a fully dual mono power amplifier; both part are separate, from the power supply -you can see on my picture 2 huge transformers- to the output. The W-5.3 is a stereo power amplifier with the power supply sheared by both channel."
as well as "I never said P-5 is better than P-5.3 or W-5 is better than W-5.3, but the power supply inside the W-5 is more sophisticated."
Although I found a forum message posted by a Simaudio person a few years ago saying this:
"With the exception of the W-5/10 (and the W-5 LE), none of the past Classic Series models was ever dual-mono in terms of power supply design. Assuming you are speaking of the W-5 (which was our most popular amplifier at the time), you do not know enough about the new W5.3 to make such a statement as "cheaper build". Furthermore, the W5.3 is considerably less expensive, therefore negating what you said that we "did not drop the price". In addition, the W5.3 is less expensive because the power has been reduced to 150Wrms/ch. With one very large transformer containing separate windings for each channel, it actually has the ability to operate more efficiently into difficult loads than the W-5 when amplifying music, because each channel can draw more than its share of current when needed - unlike the W-5 which could not. Finally, the W5.3 has all of the W-5 LE's circuit updates and tweaks, making it sound more refined and musical than the W-5. At a price of $5300 (compared to $6900 and $7800 for the old W-5 and the W-5 LE respectively), the W5.3 is, in our opinion, the better deal. "