What is your size range for "short"?
Also, what color is the house? Showy would be something that contrasts the house (e.g. yellow house so bright red bloom, dark blue house with 'white' bloom or hot-pink bloom, etc).
Me, I would always choose red (unless my house was red).
Red always contrasts grass well, even if yours has gone yellow in summer heat. I just checked and 7" red bloom Spider Man is only a 24" scape, which is a shortie to me. But it is a dormant.
Megatron is slightly taller at 30" scape, but gets you a 10.5" flower. However, also dormant.
If you can access the Jun blooms thread, look at all the ones posted by Betja, she has exquisite taste when it comes to big showy blooms. I am always overjoyed when she posts more eye candy. And she lives in a hot zone like you.