Help me - I need advice

I'm looking for a synth on which I will be able to mix all my own music. I want decently weighted keys (so it feels like a piano), enough channels so I can do full orchestrations, be able to playback from the computer through the synth (I have Sibelius for Win 95) , I also want to mix a fair bit of techno stuff. In other words, I want enough voices so I don't have to buy a separate module to go with it. If anyone can recommend places or products to check out, it would be much appreciated!
Thanks, helpjunkie