[Ron Ramirez]

I am no expert on cabinet refinishing - in fact I still consider myself a rank amateur at this stuff - but here is why I spray sealer on a cabinet before applying grain filler: because oil-based products like Constantines wood filler (which is what Constantines calls their grain filler) will stain the wood unless you apply sealer first. I know this from personal experience. And as I prefer not to have a too-dark, muddy finish, I put on the sealer before filling the grain.

Of course, the top and sides will be getting toned very dark (I assume Extra Dark Walnut Ultra Classic?), so if the wood gets stained in these areas from the grain filler, it really does not matter. But you don't want your front panel too dark, this is true.

Hmmm...your assumption about the front panel possibly having been glued in after both it and the rest of the cabinet were toned makes sense; it would seem that it would be quicker that way in production, rather than taking the time to mask off the cabinet to achieve two different colors.