The first thing that I can think of is the Socket version your going for 754. I would reccomend you get the 939 version instead as this features dual channel memory were as the 754 does not.

The Serial hard drive is very much worth getting. Again if you can use them in RAID comfiguration as this will help performance even more. For a further performance gain you may want to consider the Western Digital Raptor 10k SATA 74Gb drives in RAID, these will challange high end SCSI harddrives.

The OCZ memory is amongst the best there is, but make sure your MB supports dual channel (939) and doesn't need ECC memory (940).

I have no experience with the ATI cards but I hear good things about them, but if you r spending this much look at the newer x800 series for top notch home series card performance.

PCI-x at the moment doesn't offer any real increase in performance, no doubt that will come as the technology becomes more widespread. That is unless you use graphics cards with the SLI feature. Basically that allows you to use 2 graphics card at once, similar idea to dual cpu's.

In my opinion 64bit is the way to go if your spending top dollar on a new system. As this offers excellent performance now, and offers the best degree of future performance increases you can get for minimal extra outlay.