Regarding Roland sounds, 650 is not a big number when you take into account that good quality Midi keyboards that don’t have any sounds attached to them can cost 200-300 at least. So if you try to “get it all” from 650 synth, it will not sound professional. I’d recommend investing in a good quality VST collection that gets you started on most sounds you are going to need. One of the best options currently is Native Instruments Komplete. It is massive, high quality and best bang for the buck. In general I don’t believe you can do competitive stock music with only hardware synth. You will need to build virtual instrument collection and keep it up to date.