Forgot to mention that I would like to have stop-overs in HKG and NRT.
Based on your suggestion, I looked at SIN-NRT-LAX on JL, BA is charging $370 in taxes.

Even though I would like to use only BA miles for this trip, but since BA charges horrendous taxes for JL flights, I may consider this:
1. LAX-HKG-DPS on CX - J using 50K BA miles $174 taxes
2. DPS-NRT on CX - J class : 30K AA miles (or 40K BA miles + 53 taxes)
3. NRT-LAX on JL - J class: 50K AA miles + $51 tax

Do you think this is the best redemption ? or any better ideas ?

also, does any *alliance allow stopover with 1-way award ticket ?
thank you.