I don't know who makes them, and I actually got them for free from a friend who got a huge pack for next to nothing...
But I use red sable as my main brush, unless I'm working with metallics. You always want to use synthetic for the metallic paints, because that kind of paint is just a bit to hard on natural fibers.
Honestly of everything you want to spend money on, spending more on a good brush will be the biggest pay off of anything you can get. They keep their point better, clean up better, give you better control and so on.
As i've improved, I've found I really appreciate a brush with a longer tip, it holds more paint and since you're typically dealing with fairly thin paint it drys out fairly quick. Longer tip means more paint, which means more painting before you have to go back to the palate.
The army painter line is pretty good, and I've used a lot of those. I've also used Citadels synthetic, but those tend to be the brushes I abuse the most.
For someone getting back into it, I'd recommend something like this...