intel! via chipsets just aren't as good. also, you will need a 133mhz slotket, and yes, there is a difference, stick with the ASUS 370-133 or the new Iwill slotket, avoid Abit (it'll hold you back on certain high bus overclocks).
also, running your AGP out of spec (89mhz) is not necessarily a bad thing, especially if your video card can handle it! since you don't have AGP 4x, running your AGP at 89mhz gives the same bandwidth as about AGP 2.7x. (yes, this is true, do the math, Tom's Hardware said the same thing during their Overclocked AGP / BX133 project). if it can handle it, free speeeed!
duron is cheaper, but i wouldn't buy one still. the motherboard you have is better (BF6) than any AMD board, mostly cos ... there isn't a good chipset.