King of N,
There's a big difference in size and cost between Tennis Ball and Baseball sized cups. I had Softball size Super Jumbos for a long time before downsizing several times and settling on Tennis Ball size. Not that those are the only loads you can use, but it seems that we've resorted to sizing cups by what sporting balls will fit.
Moves that are comfortable with TB size can be nearly impossible with larger cups without flashing or fear of dropping.
Don't worry about visibility. From a moderate distance they won't notice a half inch or so in diameter. We only know the difference because we're the ones handling them. The audience really doesn't care one way or another.
You'll have to dig a little deeper. With the exception of the Penguin Cups you already have, no other cup of any quality will come close to the $100 mark. I'd expect $150-$250 would be a more reasonable figure if you really want to upgrade.
Another good resource not yet mentioned is www.cupscon.com
It's where cup collectors and performers gather to swap tips and talk about possibly the oldest trick in the world.