Have you looked into, the iOS route, ( iPad, iPhone or iPod Touch ) the reason is, if you already have one of these, there are controllers that are very stage friendly and you will have a ton of sounds at your disposal. look at a few of them here
I know this is not what you asked about, but it maybe an alternative for you. some of these controllers come with soft synth apps. that have some amazing sounds, and also have samplers that you can load your own sounds to.
I like the Novation
and the Arturia
controller,and also Garage Band has some pretty good sounds as well.
Hope this helps.