Even though, 64-bit hardware can be as cheap as 32-bit stuff today, your own real box may still be a bit out. In the meantime, here’s an affordable way to build your own 64-bit box from scratch.
All you need is a printer, preferably color, a pair of scissors, some talent in folding paper or cardboard and a bit of glue. Printing it in landscape, any size will do. Depending on your scalability needs (and your printer) it can be transformed into a mainframe type box with only very little additional resources and effort.
As you can see, multiple processor architectures are supported. Further it is stackable, rackable, can easily be combined to clusters (HPC?) and server farms. Putting smaller boxes into larger helps satisfying your consolidation needs.
No benchmarks and performance tests have been made so far. I know for sure, once it’s build, it does not consume any power and the model does not require any cooling.