I'll give you that I forgot about nVidia's new chipsets, but it's not like they are knocking down the market with them at this time. Also, I for one would not go out and buy thier first generation product, especially if stability and reliability are at stake.
As for SiS, their chipset may be great but who is offering a good board using it. Half the people on this fourm spend their time bitching about their ECS K7S5A giving them headaches.
If you go the dual Athlon route don't forget about the beefy power supply needed to run two of those babies, I bet those are a chunk of change. Not to mention that hardly anyone runs software at home to justify or even utilize two CPU's. And if dual CPU's are required I would trust a chipset from AMD.
In the end I stand by my opinion, there are a lot of half-assed looking AMD platforms out there. Every review I have seen of the P4 with Intel i845D DDR or i850 RDRAM platform says it is rock stable. To me that is worth it over the extra couple percent of performance.
There is your break.
BTW I currently have an i440BX running with a 133Mhz FSB and a PIII for two years with no problems, yeah it's old but I'm looking forward to a Northwood based upgrade later in the year. I have a VIA KT133 setup with a Duron in the other room that constantly needs new 4 in 1 drivers and is plagued by minor issues.