Would Jadis Orchestra work for Dunlavy IV?

It might work, but if you use EL34s instead of KT88s, 6550s or KT90s, you probably won't have the bass control you want. I used Jadis JA-80s (50-60 watts) on Duntech Princesses (pretty much the same speaker as the SC-IV) for years and gave up a bit of bass control for the glorious midrange, and it filled up an 18 by 20 room pretty easily. A DA-60 would be similar to the 80s in terms of power and might be a slightly better match than the Orchestra. I also am of the view that the Dunlavy designs sound better with tubes, so I think you might like the sound you get. The best sound I ever heard with Dunlavy SC-Vs (admittedly on material without a lot of deep bass) was with a VAC Renaissance 30-30 amp, so they can be driven with that power, you'll just not be able to listen at head-banging levels.

As much as I like the Cary products, the Jadis is a different league in terms of refinement, in my opinion. If you've heard the Jadis midrange you'll know what I'm talking about--there's a naturalness to the Jadis electronics that is very rarely heard. SC-IIIs might be a better match for the lower powered integrated, as they don't have the lowest bass that puts more demands on the amp, but I still think that it will work with your IVs as well, just don't expect bass "slam" or particularly tight, well-controlled bass (it will be full, though), especially if you use EL-34s.

I wouldn't be surprised since, of all the Jadis amps up to the JA-200, the JA-30 had, in my opinion, the best bass performance. And I do like the DA integrateds even better than the Orchestra. They should let you take it home if you agree to buy it if it works in your application. Let us know how it turns out.

I agree with Joe (Trelja) about the interconnects, we really would need to know your preferences before we could recommend anything, but save them for last after you've lived with your choice of amp for a while.

DA30 vs. 60?--well, I have heard the 60, and it is close to the sound of my old JA80s, which is what it is closest to in terms of power. FWIW, I have always liked the JA80 best of the Jadis line, with the 30 right behind it--the higher-powered amps are leaner-sounding than the lower-powered ones, and I feel the 80s struck the right balance between sweetness and power, even though I admit they do sound "colored" next to most other equipment. The DA60 should easily drive the Dunlavys, though it will probably be a little full in the bass, depending on the tubes you use. Given Joe's experience with the DA30, you really should insist that the dealer give you a chance to listen in your system before buying, though you can certainly narrow down your choices with an audition at the dealer's showroom. The JOR with KT88s just might be the best choice for you, and at a significant cost savings as well.

As far as tubes go, stick with the stock ones they give you for a while to see how they do before you start tube-rolling. My preference (and recognize that I like a lush sound for the most part) is for NOS Gold Lion KT88s, which combine the virtues of a midrange almost as seductive as with the best EL-34s, far more bass than the EL-34s and as much as 6550s, and tremendous longevity (every 6550 or EL-34 I used in my JA-80s would start going bad and popping their fuses within a year, but my Gold Lions were still going strong after four years, so you pay a lot for them but they last longer). 6550s are sort of OK in that they do bass with some tightness, but I always felt they robbed a little of the midrange magic that is the Jadis strength--however, if you can get some genuine NOS Tung-Sols, then you will be quite close to the Gold Lion sound for a lower price. KT90s, while initially sounding clean and dynamic, ultimately just wore out their welcome--I felt they lost too much in the way of harmonics in the midrange; Joe's description of "colder" is an excellent one. I consider them to be a slightly better 6550, but not my cup of tea. And if you just want midrange, EL-34s are the ticket, but with SC-IVs I'd recommend against them, you're losing too much bass control in my view. For input tubes I used both Mullards (a little leaner and "faster" sounding) and Telefunkens (more balanced in the full frequency range to my ear) in my JA-80s and in my old JP80 preamp, those brands are my favorites in Jadis equipment, the EIs running third, similar in sound to the Teles.

And despite what Joe implies (I consider him to be a friend and a very nice guy as well), I'm really not an expert on Jadis, but I have had a lot of time living with their products so I can try to pass on what I learned by trial and error, mostly.