Worth mentioning is that if all your doing is playback, and not actually playing the synths, then think about changing to what I've always done to solve any live playback issues . I just make exports of the songs as a wave file and playback using winamp. I have never had an issue and I think it's better as you can perfect your mixes so each song will be balanced properly.
There is no fuss at the gig, and my laptop does not need to be anything special.
You can read about how I operate here:
http://www.cactusmusic.ca/johns_rig.htm I tried the Sonar playlist thinking about using midi to control my effects and it's just way off base compared to what I'm using.
Note: I had perfect midi playback in 1985 with an Atari and Jeff Koftinoffs Pro Midi player. Set lists, Footswitchs control and Lyrics.
http://www.jdkoftinoff.com/main/Historic_Projects/The_Pro_MIDI_Player/ I think we solo performers are such a small market these day's that nobody is writing any software that is perfected for us. What Jeffs player did was perfect. All that would be needed is to add a stereo audio track to bring it into this century.
The solo or small bands wish list for a playback DAW It would be a simple stripped down DAW. It would have no editing or composing features. It would be as an add on to your regular DAW so you create the songs in your regular DAW and then save and open them here where you set them up for live playback.
Audio tracks. Could be limited to a little as 2.
MIDI tracks could play synths and control midi capable hardware. effects, lighting.
Live input to soft synth
Slots for ? synths
Effects for Vocals and guitar optimized for live ( low latency)
OK most DAWs can do the above but they are overly complicated and they can't do this:::
Playlist:
Playlist that is drag and drop on the fly and can be saved.
Stops after each song plays
Hot keys for start, stop,advance, back& pause so a usb or midi foot-switch can control.
Lyrics pop onto full screen while songs plays ( Jeff's player did this in 1984)
The DAW that adds this feature will get my money for sure.