My newcastle, actually it's termed paris in CPU-Z since it has a A64core with great ocing but only 256k chache(2.4 at stock, 1.8ghz at 1.2V, offically termed a 3300+ and i got it DIRT CHEAP(OEM), cost me a little more than a 3000+ Newcastle and chache tests show performance impact is pratically nil) but it runs very cool. 36*c idle and around 48-51* load no oc. It runs well and lets face it, for those like me that replace machine rather than upgrade or dont upgrade yearly, 939 isnt needed.
754 is perfectly capable and you dont need 939 to be happy. Get a S754 pci-e NF4 mb and a decent video card and be happy with it.