I know you don't need the 64 bit version, but I thought that going with a 64-bit OS would be the way to go.
Not yet...there aren't enough applications around that use the 64-bit instructions/extra registers to make a 64-bit OS justifiable (unless you are planning on running a server, in which case there are a number of 64-bit applications that may be of interest to you). Also as already noted 64-bit drivers can be hard to come by. If you only need chipset and video drivers then you probably won't have too much trouble finding things and could go to 64-bit Windows if you wanted. However, if you have an older PCI device (like a wireless card, or a TV capture card, etc.) you'll likely be unable to find any drivers to make it work under XP-64 right now.
how much faster would the 3000+ Venice run compared to a 3200+ Athlon?
I think you may be a bit confused by the nomenclature here. A 3000+ Venice is still an Athlon (well, Athlon64 anyways)..."Venice" refers to the core revision that it has. I assume by "3200+ Athlon" you are referring to a 3200+ Winchester based Athlon64? If this is the case, then the two will perform about the same at stock settings (the 3200+ will still be slightly faster). When overclocking however, the 3000+ Venice based chip should let you hit a higher clock speed than the 3200+ non-Venice...so it really depends if you plan on overclocking or not.
Anyways, on the original topic, I personally think now is a bad time to be buying PC components (most notably CPU's and graphics cards) unless you absolutely need a new/faster system now. Dual-core chips have just recently become available, but they are still very expensive. Similarly, nVidia has released its next-generation chip, which should shortly drive down prices of the 6xxx parts, and also ATI will probably follow suit with its next-gen chip sometime soon, and this should drive down the cost of the 7xxx nVidia parts (and of course the costs will naturally come down over time). If you can afford to wait a bit, I'd say give it about 4 to 6 months (until around holiday-time), and then you should be able to pick up an Athlon X2 4200+ or 4400+ for in the neighborhood of $200 or so, and a 7800-class graphics card for about the same.
