I would say right this minute the OEM Phenom II X3 740 BE.
I just ordered one at newegg for $68.99 (free shipping).
It was $20 off on the Thanksgiving day and 2 more days sale.
Actually I was wondering whether I should order it as I ordered a $120 1920 by 1200 pixel 23 inch LCD monitor on sale last night (It was $90 off).
I voted the Athlon X3 455 in your poll BTW because you didn't have the 740 BE.
However if it wasn't on sale the Passmark website has a list of the top performing vs cost CPU's.
The Top five in order was the Phenom II X3 740 BE ,old Phenom X4 9850BE surprisingly,and the Athlon X3 450,the Phenom II X4 940 BE (which I really like) and the Athlon X3 425.
Of course that's the today's price. http://www.cpubenchmark.net/cpu_value_available.html