except for the XV/SRX series, their successor. Seeing as you asked for 'the best' it's hard to say how far you want to go. XV synths expandability encompasses two SRX and two JV so you could have your pick of the best orchestral set, with sufficient onboard to begin with.
On the other hand, to get 'the best' orchestral sounds and stay within ur budget, maybe you can get a setup with a controller keyboard then have your choice of the best orchestral moduke, like the jv mentioned, srx, or yamaha/kurzweil etc. Try and hear the patches for yourself in any case.