I think Ed is spot on. I'm also a synth player but not very educated in the proper use of bass pedals. I've used pedals much as Ed describes, either for use as additional midi controllers or occasionally as drum pedals when I've dabbled a little on an electronic set. I've also used them on occasion with an organ, but it's far from being my forte.
I won't suggest the computer route either, although I do use mine live with no issues. There is a pretty big learning curve there as opposed to plugging in a synth and jamming on it. I like the Motif ES as well, especially with the AN plug in. That's my ahrdware setup btw. Even that might be a bit of overkill though if you'll never need or want to use the vast array of acoustic sounds in it.
A Korg DW8000 would do fine, but remember that this is now an old synth and will be subject to the problems that many of the vintage gear of it's era now has, mainly that controllers and keys tend to get sticky or scratchy, and that it's a bear to fix when it breaks.
If you want to go "on the cheap" and as you say, you need only a few staple synth sounds, you might conside something along the lines of the Yamaha SO3 or Korg X5D. Both of these are entry level synths. Although I like Yamaha's acoustic imitations, I usually prefer Korg for some of the basic synth sounds, keeping in mind that these are digital replications and not true analog sounds. In a live setting, for most players, that probably won't make enough of a difference that it justifies taking a chance on using true vintage analog gear.
AJ
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AJ