I like Doc's suggestion of the 80+ two stage VS unit. I'd have a heat pump installed verses a straight AC because it will allow you to take advantage of the cheapest utility at the time. This season gas looks to be expensive so the heat pump will be your better option. Gas heat is more comfortable at lower outdoor temps so you always have the option of switching over. Since the gas heat will only be used in unusual situations for Texas and the heat exchanger is less restrictive on an 80+, I'd use the 80+ and Heat pump combo.
P.S. I'm also a Rheem fan. Simple and quiet.