For $100 the 3.0 Ghz AM2+ Phenom II X4 940 BE is a great deal especially if you have an AM2+ motherboard.On a new build going with the older AM2+ motherboards and DDR2 RAM isn't so bad except for upgradability issues.
Even if one had a AM3 motherboard/DDR3 RAM and AM3 specific CPU's one might find out that it is just not worth it to upgrade the CPU in the future when AMD will have newer (i.e. Bulldozer) CPU's working on newer type motherboards.
Here is a benchmark comparison between the Phenom II X4 940 and the Athlon X3 440.http://www.anandtech.com/bench/Product/80?vs=119
BTW I just recently built 2 AM2+ 785G type motherboard budget systems and on one I did choose the Phenom II X4 940 BE CPU for one of them.The other system I used a spare Athlon II X2 240 CPU for that one.