The best way is to use reverb. Most relatively close miked stereo instruments work best in orchestral setting when they are panned to narrow stereo or nearly mono. A real instrument in a concert hall is practically a "mono" source which is spread to "stereo" by the hall acoustics. Stereo samples are nice for in-your-face effects but in orchestral music they don't have much advantage over mono samples. Mono can be even better as there is no phase cancellation (when panned narrow or summed to mono) or other problems related to the use of multiple microphones.