It highly depends on the mare and her bloodlines which stallions are ideal. As well you will want to go with a stallion who is approved in the same registries as your mare in order to ensure a brandable and registerable foal.
There are lots of "warmblood" horses floating around who were not purpose bred, or well bred. Lots end up at meat markets. Unless your mare is something worth breeding and you have the resources to bring the foal up properly, I would suggest against breeding.
I am located in NSW Australia .It is not our mare but one of my friends who breeds thoroughbreds the mare has the 8 carrot bloodline if anyone has heard of that before, she has a very good tempered. I want to breed a tbxwb as I want my own horse I have raised and trained. :)
Lots of nice warmbloods in NSW. Regardez Moi seems to produce a nice type [Rubenstein bloodlines]. Another of the Ryans' stallions, Jive Magic [by Jazz], is very studdy but what I've seen of his foals have been nice, that being said I haven't seen much and it does depend A LOT on what the mare is like. I like Fiji R a lot, sweet stallion and very quiet, but haven't seen him in action. There are a LOT of imported bloodlines in NSW and some of the stallions that larger-scale breeders there have imported are from among the best bloodlines in the world.
However if you want a dressage horse a purebred warmblood is probably your best bet rather than using a TB mare. I like the wb/tb crosses for eventing more than for dressage. I haven't met one yet that had quite enough movement to be competitive in the upper levels of pure dressage. The TB has, IME, a tendency to flatten them out a little bit.
There's also a HUGE range in quality in the Thoroughbred breed and a TB with good lines for racing is not necessarily going to be any good as a dressage broodmare. My filly is apparently reasonably well-bred, but that's for racing. Different discipline altogether!
Breeding is a crapshoot, why not look at buying a weanling? That way you get the gender and colour you want and you're not risking ending up with something with wonky legs. Or a stillbirth. I'm not sure which would be more heartbreaking given that breeding to a good warmblood stallion for a dressage horse will cost a LOT of money and wonky legs do not a dressage horse make!
She won the gold Olympics for dressage freestyle, she is an amazing dressage rider. I personally prefer carl Hester. BUT back to my post have you or any one heard of smash hit, sire is Sandro Hit and dam is full sister to Rubinstein.