I didn't look at all the breeders you've listed but the ones you listed that I am familiar with amount to lots
of breeding, very few titles, and vague to patchy health testing.
And the "Intl. Ch." title through the IABCA that some of them are touting is basically a bought title. Your dog doesn't have to ever win against any other dog in order to be awarded the title which can be obtained in a single 3-day show. You show up with your dog, enter the ring, the "judge" hands you a certificate. Do it three times and congratulations, you're the proud owner of an "International Champion."
Its a far cry from the competition of the AKC breed ring, or even UKC ring in many breeds and areas of the country. Some breeds are more competitive in UKC but, in show line Dobes in the US, the AKC breed ring is the gold standard for truly competitive, well bred dogs. So, I'd be looking for breeders with dogs listed as AKC CH or GCH (Grand Champion - there can be different levels of GCH now, GCHB is Bronze, GCHS is Silver, GCHG is Gold, and it maxes out at GCHP, which is Platinum).
The letters that appear after some dogs' names can indicate sport titles, like - CDX (companion dog excellent), UD (utility dog), MX (master agility excellent), NAJ (novice agility jumpers), CA (coursing ability), HT (herding tested), RA (rally advanced), SINE (scent work interior novice elite), TD (tracking dog), IPO1 or now IGP1 (first level protection sport title) and many, many, many, many, many more.
And certificates earned - things like THD (therapy dog), CGC (canine good citizen), WAC (working aptitude certification), LC (longevity certified - indicating a long lived Dobe).
ROM, or the Register of Merit, is a title awarded to Dobermans who have earned (1) their AKC Championship, (2) an approved working title, and (3) passed the WAE (working aptitude evaluation). This distinction will also appear after a dog's registered name.
Dogs can also earn sport championships, and these will appear in front of the name. So, if you see an OTCH, MACH, or RACH in front of a Dobe's registered name, that indicates an Obedience Trial Championship, Master Agility Championship, or Rally Championship, respectively. And some dogs have earned a MACH multiple times over which can be determined by the number that follows it like, MACH3 or MACH10.
As an aside, I would strongly recommend reading and talking to experienced Dobe owners a lot about health in the breed. Its better to know about the risks upfront before you bring a pup home.
Anyway, there are many good breeders in the US and some of them are right there in Texas. I second the suggestion to get in touch with local Dobe breed clubs.
You might also want to search the DPCA Breeder Referral
and the UDC Breeder Listing