Yes, the DGX670 represents the pinnacle of bang for the buck Yamaha arranger (it's essentially a stripped down CVP701, which launched at nearly $3600 CAD in matte black, just over $4k for the PE (and that was 11 years ago, it's gone up since) so the DGX represents an incredible bang for the buck. Yes, the DGX670 keys are noticeably better than even the DGX660 keys.
There is one flaw, that I find odd nobody here has encountered (but all of our customers noticed, and I simply tell them to use headphones or *don't* play at full volume if you're playing fortissimo), but the amplifiers aren't powerful enough for the speakers. So playing at full volume, even *just* the piano, if you play fortissimo, the speakers will crackle. That, and the lower CVP701 /PSRs770/PSRsx600/DGX670 sound library compared to the higher end PS500 (and speakers powerful enough to play at any volume, any strength, and they don't crackle), which shares the same sound library as the PSRs970/975/PSRsx700/CVP705/CSP1xx series, which is a huge step up from the previous (DGX670) sound library. But it also costs nearly double the 670, so there's that.
Mark