Intel CPU question

I'm confused here :confused There's the Pentium D series, the D925, D940, etc., and they are dual core. Then there's the E series, the E2140, E2160, E2180, and those are dual core also. Both the D and E have the 800FSB. The D series tend to cost a bit more and have speeds from 2.80 to 3.40 or so, and the E series have speeds like 1.60, 1.80, 2.00, etc... what gives? I know the E series chips are newer... which ones are better? The D925 is 3.0ghz, and the E2140 is 1.60ghz, and the price of each is almost identical. And the E2160 is 1.80ghz and the price is just a bit higher.... what's the deal? They all have the same (or VERY similar) caches.... Can someone help me understand this? If your mobo didn't support Core2Duo CPUs, but did support both the D and E series, which would you get???
Thanks!

 

The D series are Intel's early dual core CPUs. The lower # E series are the Core Duos and the higher E series (e4300 and up) are the core 2 duos. Check these charts out for comparisons: http://www23.tomshardware.com/cpu_2007.html

 

I would go e series . Less heat and better performance due to pd series still using netburst architecture