I need a little help understanding the BIG differences other than raw CPU speed on the aforementioned processors. I'm only concerned with socket 775 processors in this comparison. I'm mainly interested in gaming performance and I realize other components will have some effect so let's set some knowns.
 
ECS PT890T-A mobo that will support 1066 FSB
At least 1 Gb of DDR2 RAM
nvidia 8600GT PCI-e graphics card
 
Let's take a:
P4 3.0 Ghz (530J) 1 Mb cache    versus a
Pentium E2160 Processor - 1.80GHz, 1MB Cache, 800MHz FSB, Allendale, Dual Core     versus a
Pentium D 920 Processor - 2.80GHz, 4MB Cache, 800MHz FSB, Presler dual core   versus a
Core 2 Duo E6550 Processor - 2.33GHz, 4MB Cache, 1333MHz FSB, Conroe
 
Is the Core 2 Duo the hands down winner here or will the others, which are considerably less expensive be that far behind in performance.
 
What is the difference between the "dual core" vs the "core 2 duo" processors?
 
Thank you for any insightful, realistic replies.
 
gdb 'aka' dabassman

well looking at the cpu charts http://www23.tomshardware.com/cpu_ [...] &chart=425 the core 2 duo is about 4 times faster than that pentium4. the slowest core 2 duo will easily beat those processors. you should definetly go with the core2duo and at least 2gigs of ram for new apps and games.

For reference, Pentium 4 < Pentium D <<< Pentium Dual-Core < Core 2 Duo.
 
Note very carefully the distinction between the Pentium D and the Pentium Dual-Core.

The Pentium Dual-Core is based on the Allendale core, which is also used in the Core 2 Duo E4x00 line (not the E6xx0 line). It has limited overclockability when compared to other Core 2 Duo's because it is picked from the bottom of the binned pile.
 
The Core 2 Dup will win in terms of speed here, murdering the Pentium 4 and D and respectably outpacing the Pentium Dual-Core. It also has the most rewarding overclock.

The 6550 is also the best "deal" right now in Core2Duos.

 
I'll make it simple:
 
Pentium D = two P4s
Pentium Dual Core = Core 2 Duo with less L2 cache.
 
The Pentium D 920 is two Pentium 4 620s put side-by-side under one metal heat spreader. The 530J will probably be roughly as fast as the D 920 in single-threaded tasks, if not edge it out by a hair. The D 920 will be faster than the 530J for multithreaded applications. The D 920 will be a little warmer than the 530J at full-load.The Core 2-based Pentium Dual Core and the Core 2 Duo are much faster than the P4 530J and PD 920. The 1.8 GHz Pentium Dual Core will outperform most every P4 and Pentium D out there, except for maybe the 3.60, 3.73, and 3.80 GHz units. It will do this while throwing off 2/3 to 1/2 as much heat as those chips as well. The Core 2 Duo E6550 is the fastest CPU on your list by quite a bit and isn't excessively expensive nor run much warmer than the Pentium Dual Core, so that's what I would spring for if you want to spend the money to get it, otherwise the Pentium Dual Core would be a good budget chip. Forget the Pentium 4 and Pentium D.
 
Two more comments: One is that the E6550 is a 1333 MHz FSB CPU and you'll need a motherboard that can support the 1333 MHz FSB. If you want to use that ECS motherboard you picked, then you should look at the 800 MHz FSB and 1066 MHz FSB Pentium Dual Core and Core 2 Duo E4000 series and E6000 series, not the E6*50 series. The second is that you will want 2 GB RAM if running Windows XP, 2-3 GB if running Vista 32-bit, and 4 GB or more if running Vista 64-bit. RAM isn't that expensive any more and it really will make or break performance.

Thanks to everyone who took time to give an answer. I have been enlightened considerably on the diversity of Intel's offerings. Sometimes it's pretty dark in the 'forest'.
 
Happy computing!
 
gdb

Will the following laptop configuration play most current games?
 
Processor
Intel® Core™ 2 Duo T7250 (2.0GHz/800Mhz FSB/2MB cache)  
Operating System:
Genuine Windows® XP Home Edition   XPHOME  
Memory:
2GB Shared Dual Channel DDR2 SDRAM at 667MHz, 2 DIMM   2GB2D   [311-7263]   3  
Hard Drive:
120GB 5400RPM Hard Drive
Video Cards:
128MB NVIDIA® GeForce™ 8400M GS  

 
It will, but at at lower resolution than you'd probably like. The 8400M GS is not a very powerful card but the CPU rest is okay. You might want to up the HDD RPM to 7200 though.

 
Well that sorta depends.
That chip can hit serious FSB issues w/o too much of a problem.
 
Some old THG P35 reviews showed lots of FSB walls for the Mobos at just over 450FSB.
If you set the FSB of this chips to 450FSB, the CPU will only his 3.15 Ghz.
 
Many of the 1066/800FSB chips will easily OC past this mark w/o while staying well below the 400FSB.
 
You will likely need a better mobo, better ram, and other stuff to get this chip very high.
 
I think the E2140 ($70) and E4500 ($127) are likely better deals.  
Both are cheaper with the E2140 easily cruising to 3.2 Ghz and coming close in performance to a 3.15Ghz E6550.
 
The E4500 should clock to 3.2-3.4 Ghz of higher and also come even closer is not surpassing the other chip due to the lack of a FSB wall.
 
For the 1333FSB chips, I would start with at least the E6750 to make reaching the top speeds of this chip much easier. (3.6 Ghz on a 450 FSB wall)
 
Now, even if you are going to get some Good DDR2-800 RAM that can acually hit DDR2-1000 speeds and a Mobo that you know will hit 500FSB w/o a problem, you are still only hitting 3.5 Ghz on that chip.
 
The E6750 will hit 4.0Ghz on the 500FSB.
Now 4.0Ghz is pushing a little and perhaps 3.8Ghz is closer to a reasonable OC for this chip, but we are atleast starting to see some real seperation from those lower end chips.
 
However, it's all judgement.

 
Would it help if I switch the video card to a 256MB NVIDIA® GeForce™ 8600M GT?
 
Thanks for you help!

Yea an 8600 is much better than an 8400/500, which in turn is worse than the 8800 series...