esd - TVS Diode selection

I am designing a motor controller for a 24V 2.2KW d.c motor but I have a problem. I have been unable to get the 1.5KE39CA TVS Diode spcified in the design guide i am following. But i have two alternatives:

1. 
   
   

   A Z2 033 TVS diode (say D1) found here and

   
   


2. 
   

   A 1.5KE18CA TVS diode (say D2) found here

   
   

D1 is rated 33V (Breakdown voltage Vbr), but has Peak Pulse Power of 500W. D2 is rated 17.1V Vbr and has Peak Pulse Power of 1500W. (same power but different Vbr as the 1.5KE39CA)

Can i combine two D2's in series to get a total of 34.2V Vbr and 3000W Ppp (as described here) or should i use D1 the way it is (because this material claims the Ppp is not of utmost importance )? What is the implication of either method?