Foster_9,
Was not aware of impedance matching being the source of problems with the lower bass reproduction with that player. But I just read the preamble for the Stereophile review posted on the PrimaLuna website - yes, looks like they acknowledge that there is a problem with very low input impedance preamps.
In any case. John Atkinson noted in a subsequent discussion in the magazine that the upgraded OP amp boards did improve the upper bass noticeably and with the board installed in his words "the PrimaLuna becomes a straight Class A recommendation." He also noted in his first look at it that "it threw the widest, deepest soundstage from CDs that I have experienced with any player". Hmmmm, strong statement.
I should provide clarity on the cost of the board upgrades: The Super I/V OP Amp kit "Basic" is $150, the Super I/V OP Amp kit "Plus" is $235, or a difference of $85 between the two. If you are investing that much for a player, I would pay the roughly 10% extra and get the "Plus" upgraded board.