Taurus has several great 9mm's that can be bought in the mid to upper $300's. EAA is another, Bersa or Kel-Tec. If you move up to the mid $400's your choices will expand quite a bit. I like the XD best in the under $500 price range. I have no use for anything that says "Glock" on it.
These are just suggestions and my opinion. Best to try as many guns as you can yourself and decide based on your experience.
My only personal experience has been with the Bersa Ultra Compact (13+1) & the Hi Capacity (17+1). Sweet shooters, reliable & accurate. The aluminum frame holds down the weight & will balance differently than all steel, but feel good in my hands. The finish is not the greatest, but just means I don't have to be so concerned about holster wear.
It's crazy how I hate the sigma and think the m&p is ugly but I love the sd models.
IMO the sd models are the love child from the two. They took out what people hate about the sigma(glockstyle,heavytrigger,sloppyfit/finish) and put in the great parts of the m&p(better trigger, better finish. And then the looks are a hybrid of the two. I love the gun and the price tag even more!