http://arstechnica.com/guides/buyer/system-guide-200506.ars 

What is interesting is that the budget box solution is now based on AMD64 939 and PCI-Express. Hmmm... maybe it's just me, but I would prefer a more conservative solution based on the omnipresent 754 socket and AGP 8x. For example, older VIA K8M800-based motherboards with the good old AGP 8x and integrated on-board video might do the same job as well.

While I believe that PCI-Express is just taking off and PCI is still the dominant technology for all the cards, it is interesting that you already find cheap motherboards like MSI RS480M2-IL based on the ATI Xpress200 chipset at such low prices...