I'd respectfully advise to stick with the 1.2 Ghz and save the $10.
The 1.3 Ghz would not give a linear increase in system speed over the 1.2 Ghz. In other words, your system performance won't increase 7.6% as implied by the difference in clock speeds. Mr. LaShrimpi would agree that this will only provide between 2 to 3 percent system improvement because of the CPU's dependence on so many other things such as memory, hard drive rotational speed, video card memory......etc. So do the Math:
Assumptions:
CPU costs $60
Mobo cost $55
The 1.3 Ghz CPU would cost 14.3% more than the 1.2 Ghz for only a 3% (at best) system performance improvement.
Why not save the $10 and put it towards your upgrade to the 2 Ghz XP or MP later when they also come down to $60 or $50 or $40.....
BTW, I'm using a K7S5A & 950 Mhz to write this reply. Kind of a testy board, but once you get the bugs worked out.....rock solid baby!