Unless an account agreement requires it, there is no Reg. E or Reg. DD notice required for a change in the order in which the bank pays checks is there?

Since you restricted your question to Regulations E and DD, no.

However, I'm sure you're aware that the order of item payment is a hot button with regulators right now, and there are some guidance documents issued in 2005 and two proposals to supplement that guidance, all of which touch on the issue.

Depending on the bank's federal regulator, making a change to posting order without notice to customers could draw criticism from examiners under the wide-reaching UDAP umbrella. The OTS is particularly public about its concern.