I don't know where Alan lives but he might want to look and see if there are some small independent companies that could put this system together for a small price. If he lives in my area, I would do it in a heartbeat!!
I did just that about three years ago when I decided to move from a Dell XPS-something-or-other running 32-bit Vista up to a 64-bit Win 7 system.
I explored the build-it-yourself idea I was too timid to go that route. Instead I found an outfit called PCs for Everyone (http://www.pcsforeveryone.com/
) which had a distribution depot within an easy drive of where I live, near Boston.
The nice thing about their site is that they have great planning tools that let you start with one of their standard pre-configured machines and go down the list of specs to see what alternatives they offer to each part. They give you the exact maker and product number of each item so you can easily look for reviews to help you pick the one that fits your own needs best. Once you pick your configuration, you can either get the components to assemble yourself, or you can pay a few bucks (I forget how much it was) to have them assemble and test the whole thing. I went for having them put it together, and I drove to the depot to pick it up when it was ready.
Just to set the record straight, what I ended up with does in fact have a 24GB memory maximum, because it has six memory slots (3-channel memory) with a maximum capacity of 24GB for the whole board (perhaps I could double it now if I wanted to, if I updated the BIOS, but I've never found the need to). My system has an Intel Core I7 950 CPU @ 3.07 GHz on an Intel DX58S02 motherboard (Socket 1366 LGA). I chose an Antec "Ultimate Gaming" case because it is easy to open for adding or swapping components, has lots of fans with easy-to-remove and clean filters, and at least seven drive bays.
I have installed various hard drives and an SSD and added a RAID controller and ESATA card and cleaned the filters a few times, and it has run beautifully for me.
A local "white box" outfit like this could be a good way to go, unless you do live within an easy drive of Steve Weldon.