With your current normal settings, your 2-channel programs (like CDs in UPSAMPLE that you mentioned) sound good, but 5.1 programs (like audio DTS DVDs like you also mentioned) have too much sub by 6 or 7 dB. Is that correct?
Actually, his problem appears to be too
little sub with 5.1 content when the sub is calibrated to work for two-channel material. Having said that, though, your advise about experimenting with crossover points may still be of use to him.