Oops, sorry Gil, I know next to nothing myself. You don't want my system, it's based on a motherboard that probably hasn't been sold for 18 months or more. I'm just trying to extend it's life for a reasonable amount of money, in lieu of spending "much" more on a new system.
The motherboard I am using is from Supermicro, and the two takeaways I have is that your motherboard investment is perhaps the most important part of your system, and once you've priced your motherboard, an inexpensive additional investment would be to get a dual processor motherboard. I used to get those Fry's specials: $49 mobo. But I have found the Supermicro motherboard (at $150 maybe?) to be absolutely rock solid, and almost as important, and this may just have been luck, it has remained a useful system for almost three years now.
But as to which motherboard, or which chipset you should get, well that's some other guy (maybe Don), not me.
About a year ago(?) I was thinking of building an ACS site where folks could just enumerate and detail specific motherboard/controller/vendor/application solutions and how well they have worked out. Sort of a geek/niche version of epinions. And then the dotcom market collapsed and my $49M funding vanished. Yeah, that's the ticket.