Is cost your main concern? I would definitely go DDR, it will eck more speed from your proc.
I put the ECS SiS735 board in my sister's computer in conjunction with a Duron 700 and 256megs of SDRAM (it can take DDR too) . Though the board is rather feature sparse, and the integrated audio sucks, its quite stable and suits her perfectly. Last I checked, it was around 60 bucks at Newegg.com.
If I was going to pick a motherboard, I would go for either the Soyo K7V Dragon+, the Abit KR7A-RAID, or the Asus A7V266-E. I have not had the experience of working with one of Nvidia's nForce based motherboards, tho I hear the boards are quite stable and perform well. The integrated video and the audio is also MUCH better than the AC97 codec based integrated audio in other boards.