Sure, what NAD told you can be correct. Analog crossovers existed long before digital audio ever came along. If that's the way NAD says their receiver works, I'd tend to believe them, absent any other information to the contrary.
More generally, assuming you can balance the sub and sats either way, I seriously doubt there's an sonic difference between doing the D/A conversion in the CD player and the receiver (but you can always compare them yourself). So the choice probably comes down to convenience or features (such as access to signal processing capabilities in the receiver).
More generally, assuming you can balance the sub and sats either way, I seriously doubt there's an sonic difference between doing the D/A conversion in the CD player and the receiver (but you can always compare them yourself). So the choice probably comes down to convenience or features (such as access to signal processing capabilities in the receiver).