Hmmmmmmmmmm. . .
I work in the retail sector of the piano industry. I can tell you this, we stock the CLP115,120,130,150, 175, not the 170(but we still sell a lot of the CLP170's)
I guess it all depends on the market in your area. The dealer may think that the CLP130 and 150 are not worth stocking (i would disagree though)
The CLP130 looks like the 120, but does have many nice upgrades. The CLP170 looks like the CLP150 but also with several nice upgrades.
Its hard to say. Some dealers limit their stock and try to sell down from high end models. It all depends.
If you like the CLP170, I am sure you would also enjoy the CLP150. The 170 has the nicer speaker system and diskdrive, better sound samples, and the availability of the polished ebony finish. I am sure I missed some differences, but am sure you get the point.
If you like the CLP120, you would like the CLP130 even more. All features are basically doubled. Double the voices, wattage, increased ROM, etc etc. There should only be a few undred $ difference between the 120 and 130. However probably a more signifigant price increase from 150 to 170.
Hope this helps some!
Representing Yamaha, Story and Clark, and other fine instruments
Menchey Music Service
Associate Member of PTG
Serving Central Pennsylvania and the Greater Baltimore Area