Greetings Ernie,
I would add that you could easily get a 512MB video card, or get a motherboard with dual PCIe video slots, and use two 256MB video cards. The latter might actually save you some money.
To address the noise issue, you need to use a case with the best possible air flow, with low restriction fan grills. Just about the best case at this moment, is the
Antec Solo. It also has dampened side panels, excellent wire management, and a unique hard drive suspension option. The stock fan is reasonably quiet on it lowest speed, or, you can replace it for an even quieter machine. If you want to better safeguard your hard drives, by keeping their temperature down, you can use one (or two) very quiet 92mm fans in front for this.
The power supply is a source of noise: if you get a SeaSonic S12 model, or a Fortron Source "Green" power supply, you will get a very efficient and quiet power supply. 300-400 watts all you need -- more than double what a computer is likely to use.
The CPU heatsink/fan is a critical source of noise: the stock units are typically quite noisy. Good heatsinks have a lot more surface area, and work better with less air flow, and they use larger fans (typically 92-120mm) that can shift plenty of air while running slowly enough to be be barely audible.
The motherboard northbridge heatsink, and the video card are two other sources of noise: if the motherboard is not already using a passive heatsink, you can usually swap it out with an inexpensive unit, very easily. Video cards can be had with stock passive cooling, and this is the way I would go.
dual DVI passive video cards
The last source of noise is the hard drive: Samsung and Western Digital are the quietest, at the moment, and the Solo can help deal with any vibration that some units may have, with it's suspension.
In answer to a similar question on the DBUG Forum, I gave this answer, and since it may be of help, I'll post it here, too:
I have a dual core 64bit machine with both 32bit and 64bit Windows XP Pro. The only reason to get 64bit would be to make use of 4GB (or more) of RAM, and it has the downside of a dearth of compatible software firewalls, and "funky" plotter drivers. It works fine for most things, but most of the time, I boot to 32bit.
I have 2GB of RAM, which is a good amount to have -- if you need to upgrade to Vista later, you will want to be able to upgrade to even more, since Vista takes at least 2X as much RAM to run.
As for the Intel vs AMD question, the Intel Core 2 Duo CPU's are the best performing. The AMD's have slightly lower power consumption at idle, and they can cost less -- and they are certainly very fast, as well. But if you are doing any heavy duty rendering, video editing, etc., then the Core 2 Duo will be faster.
They make two basic versions of the Core 2 Duo: one with 2MB of L2 cache/core, and one with 4MB of L2 cache/core. The clockspeed is the other variable, and they all can be overclocked to a very high degree, if you are so inclined. Faster RAM is only marginal in benefit, unless you overclock.
Here's the thread on the DataCAD Forum where I am trying to keep things up to date:
http://forum.datacad.com/viewtopic.php?t=400