The 9600dpi quoted is probably the increment the stepping motor in the scanner can theoretically yield once transmitted through whatever arrangement of gears drives the scan head. Needless to say, it is a completely bogus measure. The other resolution will normally be the pitch of the linear CCD (or heaven help us a CIS).
In reality the limiting factor is the optics between the platen and the sensor. In cheap scanners, it is usually an array of pinholes, because otherwise you would need an enlarger-class lens that will focus a flat original against a 8" wide linear sensor a mere inch or so away (that's a , and that is no small feat, that's a 150 degree FOV, equivalent to a 4mm lens in 35mm equivalents).
The V750 has a real lens (2 in fact, one for flat art, one for negatives/slides), but obviously they are not in the same class as an Imacon or a Coolscan, let alone a drum scanner. The V600 doesn't have a proper lens at all (they say "the scanner features Epson's superior Matrix CCD Micro Lens technology", in other words at best a single element micro lens of questionable fabrication accuracy, sitting directly in front a sensor pixel.
I doubt any consumer grade flatbed scanner can achieve much better than 1200dpi resolution. You need a prepress scanner like a Fuji Lanovia/Quattro, CreoScitex (Kodak) or equivalent to do better.
