You should be fine. nForce2 is dual channel DDR, meaning you (ideally) should use 2 DIMMS (2x256 instead of 1x512). But I don't think you'd be any worse off in single channel than you would with the Via board.
Get two 256 DIMMs instead. Get better performance (usually), save some money and rejoice over your fancy new A78NX Deluxe and its spiffy onboard sound.