First off DO go for the 939. The 754 isn't worth the money, it's markedly slower due to the single channel memeory interface.
There used to be significant difference in performance between brands but they are all within 1-2% now. Reliability is about the same too. All you are really looking at anymore is the warantee/support and the MB features. So pick the feature set you want, find some MB's and then compare price vs warantee.
Check the vendors support website to see if the site is fast and has bios and driver updates readily available.
As for chipsets last I checked NF4 is top with VIA close behind, then SIS and ALI are a distant third.
"Top names" are ASUS, Gigabyte, MSI, ABIT (no particular importance to the order I listed them). The second stringers are ECS, Chaintek, Soltech, Aopen.
I am using, or have used every type, and the only difference between the top and second stringers is support, options and price. I've had top quality ones crap out and second stringers last forever.