Yes i believe DFI was bad back then but now they are good. Good mobo manufactures include asus, abit (very nice socket a's), and msi. I haven't tried the other manufactures yet but most left are "value" and so pretty crappy most of the time. The exception is a newer company named ASRock, they make good boards that are better than the "value" boards because they are the cheap version of Asus and i believe owned by Asus. Finding any of these good brands is hard but newegg.com has a good selection of socket a's left. most are "value" but there are two ASRocks and those i would recomend. At least they are very good as skt 939 boards one of witch i own. Here's a link to neweggs page of socket a's
Newegg socket a's
As u said you are kinda beating a dead horse, the best thing would be to upgrade to at least 754 if not 939 but if you can't and the dfi is working right now i don't think you should worry a lot about changing the mobo. The only difference would be changing manufactures, maybe a little quality, and some features. The nf2 was a good chipset back then, trust me my friend has been through about 3 different skt a chipsets and the nf2 was the best. The nf2 is now the hardest to find to and the most expensive. So i say stick with the dfi and upgrade in a year or so or upgrade now if you can.