Modern alternatives to Gaussian
"Specifically, I'm curious if there are any programs which come close to Gaussian in breadth"

Not really, as far as I can tell. Gaussian is a massive work by many, many people over many, many years, and the reason it's still one of the most popular packages, as far as I can tell, is that it does most things (notably excluding non-GTOs), even if it's not necessarily the fastest or the best at the things it does in every case.

"but also take advantage of things such as GPU processing."

Double no. As LordStryker says above, GPU programming is pretty new, and most of the resources I've seen for it are C-based, while a significant chunk of scientific development still takes place in Fortran. I suspect library-based encapsulation of GPU-running numerical routines may improve this over time (I mean, by introducing people to the idea of getting speedup by using the GPUs more easily), but I wouldn't hold my breath. It'll be interesting to see what hybrid chips with multiple types of core, or the Xeon Phis will be able to do, though.