My story revolves around a group of human astronauts exploring various planets via a new revolutionary type of drive. One of the planets I'm envisioning is a Cold Super-Venus, i.e. larger in size, mass, and gravity. While I do want a similar Greenhouse Effect with Atmospheric pressure in the 200 atm - 400 atm range, since I'm creating biological aliens to populate this planet I need it to be much cooler than Venus is. The obvious answer is to push it out way past the normal Goldilocks Zone, so the temperature range is manageable.
Any ideas and suggestions would be most welcome. Assume a Temperature range of 50F - 180F, so that biological life is plausible. The plot point is that the aliens can't leave the planet because the lower pressure would kill them, just like deep sea creatures on Earth can't survive on the surface. Any help would be greatly appreciated.