Question: Is the IPO rating a relatively sufficient mark to assure us of a quality dog or is there a more advanced level that would be a better indicator?
That... well, that's its own huge can of worms.
I'll just give you the criteria that I personally settled on for myself. (Context, in case it's helpful: once I have an opening for another dog [so probably not for quite a few years], my plan is to go for the very best all-around performance puppy I can find, with an eye toward competing at high levels in AKC sports and potentially dabbling in IPO. I want an OTCh dog, or at least a dog where the limiting factor in the partnership is my lack of skill as a trainer and not my dog being literally insane.)
-- The breeder has personally trained and trialed at least one dog to an IPO3. Doesn't necessarily have to be the dog that's being bred, although of course that would be great if it works out that way;
-- The breeder has personally trained and trialed at least one dog in AKC venues (obedience and agility preferred, Open or higher level preferred); the point here is that I want a breeder who has firsthand experience with the different environmental pressures of those venues and is familiar with the slightly different training and temperament demands of those sports. You can't always just plug-and-play an IPO dog in AKC obedience.
Sometimes you can, but not always, and I personally am looking for a breeder who knows the difference;
-- Both dogs in the breeding pair have at least an IPO1 or a CDX. This is where I'm personally setting the bar for "okay, both sire and dam have shown evidence that they are capable of excellence in these sports." You might put it higher or lower, I dunno. Coupled with my other criteria, IPO1 and CDX are sufficient for me to feel comfortable that the dogs are suitable for my purposes, so that's where I put it for my own consideration;
-- I really like what I've seen from dogs out of that program, either via
lots of videos (of both trials and training) or seeing them work in person;
-- all appropriate health tests and certifications are in order;
and
-- Prior dogs produced from this program have a proven track record of accomplishments in IPO and/or AKC venues (thereby demonstrating that the breeder is not only a decent competitor but is capable of producing dogs who can replicate or exceed the breeder's own results, and that other sport people have made votes of confidence in the program by taking their dogs. This one is important to me because I suck at puppy evaluations and so to some extent I have to rely on the judgments of others to bear out my own).
It's not uncommon for an IPO breeder to sell primarily to IPO competitors, so sometimes really good kennels won't have a lot of representation in AKC venues, and the representation they do have might not consist entirely of scores that blow your socks off. That's not a problem for me, especially if the dogs are being run by less experienced handlers (i.e., if I see a dog that's pulling mid- to high 180s in Novice A, to me that's a plus, because those are good scores for a newbie. But if I see a dog that's pulling the same mid-180s in Novice B, never goes beyond that, and the handler's other three dogs all scored in the mid-190s straight up through Utility and this dog is the only one who ever topped out that low,
then maybe I'm not quite so sanguine about that string of numbers).
All this stuff is negotiable, of course. But those are the standards I made up for my own Imaginary Future Puppy consideration.
Also, I do like all the breeders whose names have been suggested for your consideration so far. I'm more familiar with some than others, but I think those are all good recommendations.