You will be lucky to find these but if you do just go to customer service and tell them the rebate form is wrong, they will sell you the psu for $60.00...which by itself is a good deal since this unit goes for $80+ everywhere else...
just a side note, the rebate form in question has two sides one is a 20$ rebate for a case and $10 for the psu...apparently cusa corporate told them to just turn the rebate over and use the 20$ side...make sure you tell them that the 20$ rebate is for the case! not the psu...and hey if you are ambitious you could include a copy of the flyer with a note saying you are entitled to a $20 rebate!!! that?s $40 for a 400w antec psu...of course i will not endorse the last option as it smacks of fraud...
good luck...