The relevant question is, are you satisfied with the way your Cayin drives the ProAc D15? If so, either Jadis will get the job done.
I own a JOR, DA30, and DA60, and would tend to agree with Avguy about the superiority of the DA50S over the JOR, though may differ on the ultimate degree. I would say a lot of it, (predictably) comes from the difference in topology - fixed bias (JOR) versus cathode bias (DA30). That's not to say fixed bias is inferior, as I certainly don't believe that. Obviously, Jadis put a lot more money into the DA50S; reflected in their retail pricing. But, all things being equal (and, when are they ever?), a cathode bias circuit will sound more warm and liquid, though at the expense of power. Further along those lines, getting the JOR to sound the way it can is dependent on having the right tubes, and biasing it properly. While neither amp sounds its best with the stock tubes, I believe the Ei KT90 found in a lot of JORs is an especially bad choice, and hamstrings the amp tremendously from a sonic perspective.
Also, on top of the fixed bias operation, as the JOR operates in Class A/B, whereas the DA50S is more towards Class A (claimed to be Class A, but most amps that claim to be Class actually are not - I need to check the plate voltage and current, it's been a while since I had mine apart), though the more upscale product is going to be at a disadvantage in terms of power on paper, as Avguy mentioned, it doesn't necessarily translate into real world, seat of the pants power.
While both amplifiers provide for one to try a wide variety of tubes to dial in their own preferred sound, you have to take the JOR apart to bias it. That means working around B+ voltages of about 550V. So, if you're not comfortable doing so, you'd want to opt for the plug and play convenience of the cathode bias DA50S.
In the end, if you have legitimate cause for concern about power, you need to step up to a DA60 or DA88S, as the gap there between them and the smaller Jadis integrateds is quite significant. But, presuming the products at hand will satisfy the need, putting all of the above together, I would say the question ultimately comes down to your own personal taste, and again returning to fixed versus cathode bias. If you want a more open and engaging presentation, the JOR is the better starting point. If you prefer richness, liquidity, and an overall more relaxed presentation that many an audiophile will equate with, go for the DA50S.
I own a JOR, DA30, and DA60, and would tend to agree with Avguy about the superiority of the DA50S over the JOR, though may differ on the ultimate degree. I would say a lot of it, (predictably) comes from the difference in topology - fixed bias (JOR) versus cathode bias (DA30). That's not to say fixed bias is inferior, as I certainly don't believe that. Obviously, Jadis put a lot more money into the DA50S; reflected in their retail pricing. But, all things being equal (and, when are they ever?), a cathode bias circuit will sound more warm and liquid, though at the expense of power. Further along those lines, getting the JOR to sound the way it can is dependent on having the right tubes, and biasing it properly. While neither amp sounds its best with the stock tubes, I believe the Ei KT90 found in a lot of JORs is an especially bad choice, and hamstrings the amp tremendously from a sonic perspective.
Also, on top of the fixed bias operation, as the JOR operates in Class A/B, whereas the DA50S is more towards Class A (claimed to be Class A, but most amps that claim to be Class actually are not - I need to check the plate voltage and current, it's been a while since I had mine apart), though the more upscale product is going to be at a disadvantage in terms of power on paper, as Avguy mentioned, it doesn't necessarily translate into real world, seat of the pants power.
While both amplifiers provide for one to try a wide variety of tubes to dial in their own preferred sound, you have to take the JOR apart to bias it. That means working around B+ voltages of about 550V. So, if you're not comfortable doing so, you'd want to opt for the plug and play convenience of the cathode bias DA50S.
In the end, if you have legitimate cause for concern about power, you need to step up to a DA60 or DA88S, as the gap there between them and the smaller Jadis integrateds is quite significant. But, presuming the products at hand will satisfy the need, putting all of the above together, I would say the question ultimately comes down to your own personal taste, and again returning to fixed versus cathode bias. If you want a more open and engaging presentation, the JOR is the better starting point. If you prefer richness, liquidity, and an overall more relaxed presentation that many an audiophile will equate with, go for the DA50S.