I use Apple’s Mainstage for my MIDI Pedals setup when I’m playing with my band. Mainstage is part of Apple’s Logic Studio suite, and is highly customizable. The latest versions of Logic only run on a Mac.
If you are a Mac user, and don’t want to plop down the cash for Logic Studio, you can use GarageBand to create your synth sounds. There are plenty of great, classic sounding synths to choose from, or you can buy and install other virtual instruments if you’re looking for a particular sound, such as Alturia’s Analog Factory. The best part is, GarageBand comes with every new Mac.
For my MIDI setup, I’ve used an old 1.25GHz PowerBook G4. It’s fast enough to run an old version of Mainstage and GarageBand. So if you’ve got an old Mac that’s unused, try it out with your MIDI setup!