When you raise the BE multiplier beyond 'stock' you lose C&Q. You have a number of options to consider. A third-party utility like PhenomMsrTweaker
may help you.
Or you may over-clock 'old-school' by using the system clock set to 240MHz (drop your RAMs divider from 800 to 667 in the BIOS, and your RAMs will run stock spec with the system clock at 240MHz).
16x240MHz= 3.84GHz at load (or 4x240MHz - 960MHz at idle with C&Q)
Your UD5 can take the system clock much higher but you will have to further reduce your RAMs divider to 533 (if you are interested). This will require you to run you RAMs at less than stock speed (not really a biggie from a performance standpoint -- you should be able to reduce your timings to more than make up for the loss of overall memory speed).
16x250MHz will return you to 4GHz --- but at the 533 divider your RAMs will be running 5.33x250MHz, or 1333MHz. Could be a wiener for yahs ....