Real-time Software Synthesizers, Is it practical to try and use software synths on stage? Options

[Mello]

I'm a new ibook owner (192 Mb ram, 500 Mhz, 10 gig), and I plan to add the M-audio quattro to my rig soon (USB 24-bit 4 in/out, 1x1 midi connection). I've got a Kurzweil SP-76. While the Kurzweil has a good feel to it, and lovely pianos, my heart has always belonged to analog synths and organs when it comes to the keyboard. I'm noticed that the software synthesizers seem to be much less expensive than their hardware counterparts. I play bass in a band, and I occasionally play a little piano, but I don't use the Kurzweil much on stage because it's built-in organ is weak. I've been thinking about getting Native Instruments B4 hammond organ softsynth. And then choosing from the amazing number of analog synthesizer softsynths out there. I've heard there can be a bit of a latency problem. People have told me that the standard apple ASIO gives an 11.6 ms. latency, but that third party ASIOs can lower this time to 7ms. Is this a problem? I'd love to hear from people who are doing this. I don't really have an appreciation for what 11.6 ms. of latency would do to live performance. I also don't know what kind of latency (if any) you get from dedicated hardware - i.e. redsound's Darkstar. Should I be messing around with these softsynths. I really am not as interested in them for recording as I am for live performance. If any of them are worth my time, which ones? I'd love to save a little cash, but if the softsynths just can't handle live performance then that's really money wasted. Thanks for the help.