I like Bighorn the best for a synthetic/leather combo saddle. I've had one ever since I bought my first horse nearly 15 years ago and it is still in great shape. I don't ride it anymore because I've moved on to better saddles, but it's held up GREAT.
What I would recommend though is a good quality used saddle. The reason is this:
If you spend $300 on a junk saddle it will be worth perhaps $50 used (if that much, and if it doesn't break in the meantime) if you ever go to sell it.
If you pay $300 for a quality used saddle, then in a year or two when you go to sell it, you will get your $300 back out of it, because good saddles don't depreciate. So look at it that way. You can loose your $300 on a junky saddle, or get your $300 back out of (and perhaps maybe even make a profit on) a good used saddle. It just makes better financial sense.
Plus the odds are in better favor of a quality used saddle actually fitting your horse. But, if you want to go new for around $300, get a Bighorn, Wintec or Abetta. There ARE Bighorns in that price range and I think they are better quality than the Abettas. I have never ridden a Wintec but folks seem to like them.
PS. I didn't mean to leave out Fabtron, I just have never seen one in person so that's why I didn't comment on those.