Hi Datablues,
all I can suggest is that you make another comparison listening to different keyboards through a pair of good quality headphones. I own a Roland VA 7 and am quite satisfied with its sounds (many of them are taken directly from the JV/XV series). I think that the Yamaha PSR 9000/9000 Pro have excellent sounds, better than the PSR 740, but if you cannot hear the difference (not even through headphones) this means that you are lucky and can be satisfied with your present setup.
Regards
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Korg Kronos 61 and PA3X-Pro76, Roland G-70, BK7-m and Integra 7, Casio PX-5S, Fender Stratocaster with Fralin pickups, Fender Stratocaster with Kinman pickups, vintage Gibson SG standard.