E6300/E6320 (edit: & Xeon 5120) compared to P4 3.2 Ghz HT

The E6320 is essentially the newer version of the E6300. The only difference is the newer stepping and obviously the larger L2 cache. Definitely get the E6320, because they are the same price. I've seen them on newegg for around $160.

If you can afford it, you might want to go with the E6420, which is now the same price as the 6300 was when I bought it in March.

In terms of comparing it to the P4, you'll get at least the same performance as the P4, if not better. Not only is it dual core, which the newer Adobe suites are optimized for, but it is drastically more efficient than the P4 despite the lower clock speed.

You'll definitely be satisfied with a Core 2 Duo.

All of the Intel Core 2 Duos are 64 bit chips. And don't worry, you won't lose any performance, you'll only gain it. They're also much more power efficient and run cooler than Pentium 4's.

The Xeon 5120 is simply the dual-processor version of the E6320. A single 5120 will perform similarly to the E6320. I'd suggest buying a Core 2 Quad over a pair of Xeon 5100 dual-cores as the C2Q is as fast and MUCH cheaper than two Xeon dual-cores when you consider in the cost of the motherboard and expensive FB-DIMM RAM that the Xeons take. I'd only suggest getting the Xeons if you need 8 cores- that would be 2 5300 series Xeons.

Take the E6320.

There are, but they are subtle. Here they are:

1. Memory
C2D E6320: Uses up to four unbuffered, unregistered DDR2 or DDR3 modules in up to a 128-bit (dual-channel) arrangement for up to 8 GB maximum with DDR2 and currently 16 GB maximum with DDR3.

Xeon 5120: Uses up to 32 fully-buffered DDR2 DIMMs in up to a 256-bit (quad-channel) arrangement for up to 128 GB maximum memory.

Difference: The FSB is the same in both cases at 1066 MHz effective, and that is well below the maximum throughput of the RAM, so the quad-channel setup in the Xeon will be of no use. The Xeon's FB-DIMMs are more expensive, hotter-running, and have a much higher latency than the standard DDR2 modules in the C2D machine. But they come in sizes of up to 4 GB and you can use more than four on a single board, allowing for more than 8 GB for a single machine. You can put 16 GB on a DDR3 C2D board today, but DDR3 is extremely expensive compared to FB-DIMMs. FB-DIMMs also are buffered and use error-correcting code (ECC) so they are much better suited to work in an environment where reliability > speed.

2. Motherboards

C2D E6320: Uses a standard LGA 775 motherboard with a normal 945/965/975, 3000, or 33/35-series chipset. Comes in uATX and ATX formats. Upgradeable to Core 2 Quad. Price is $100-250 in most cases.

Xeon 5120: Uses a dual-socket LGA 771 motherboard with a 5000 series chipset. Comes in ATX, EATX, and rackmount formats. Upgradeable to 2x dual core or 2x quad core. Price is $300-500 in most cases.

Differences:
The Xeon board is much more expensive but is much more upgradeable. It has a current maximum of 8 cores (2x quad) and you are currently using a single dual-core CPU. The C2D board is less expensive but less upgradeable. You can put two more cores in there and that's it. I'm supposing that both are server-class boards and will use decent-quality parts, otherwise the Xeon board will likely be more reliable and be guaranteed to work with workstation/server OSes instead of just Windows Vista or maybe XP like the consumer stuff is.

3. Power consumption:

FB-DIMMs and the second FSB in the Xeon machine suck more power, so the Xeon will use more power.

That's about all I can think of off the top of my head.

This is probably due to the fact that most people won't need to address more than 3gb of ram. Unless you plan on initially having >3gb of ram memory it will actually hinder your performance to choose the 64bit version as this extended memory addressing system consumes more memory itself. Plus you can always swap your product key with a 64bit install cd at a later time.

Product keys for 32/64 bit versions of windows should easily be exchanged as long as your sticking to the OEM software sets. As this is what is shipped with the machine.