Bluezplayer, once you start down the softsynth and soft arranger route you will never return to hardware - studio or live performance. The sound alone will overwhelm you. Yes, the control surface needs some work but you can easily get used to it. This is motivating me to continue enhancements on my system - wow!!!!
If you want to start with a relatively good sounding arranger system then sYnerGi GS would be a good start for the arranger sounds. You may need to adjust the volumns a bit but generally the Yamaha styles will sound fairly good. I wouldn't use the Yamaha SW1000XG soundcard - way way way way to much latency plus the sounds are not very good. It is better to use something like a softsynth and the above noted wavetable. For the melody/lead voices use something like Kontakt and professional instruments, e.g., VRSound Saxes, Bardstown Bosendorfer Piano, etc. or the softsynths you plan on getting.
You can tie all this together in a nice streamlined and efficient package with Brainspawn's forte Ensemble. You can load this and OMB or Live - Styler with the launch of Windows and be ready to play in 30 to 60 seconds. You can even include a vocal harmonizer in this setup. It works and works very well. I am operating a modest computer by today's standards at 3ms latency and computer usage at 55%.
The good news is that each person will build their own unique system. It doesn't get any better than this!!!