I am currently running an AMD Phenom II 940 with 8 gigs of 800 DDR2.
Now, I rip and burn blu rays, but I have to re-encode them to fit on a dvd+r. With my amd athlon 64 4800+ dual core, it would take about 5-7 hours per movie. With this new setup, it takes 3-4 per movie. And it dont bog my system down. Also, if I use task manager and put all resources to the re-encoding, it dont bog my system down much either and thats setting it to realtime.
Just make SURE you get a MB that CAN support the 940. I originally bought an ASUS model that said it did, but only the 920, not the 940. I went through hell trying to figure out why that processor would not work, I tried everything and I mean everything. After I Was done trying everything, I took it to my local computer shop to have them look at it and told them everything I did to check it. They had it for three days before I finally called them and told them that I called ASUS and they told me that it wont work with that MB. Needless to say they didnt charge me, but I updated bios, changed ram around, went with no ram, little ram, max ram, no vid card using onboard, with vid card, with no hd or dvd and with and every combo of all that you can think of. I finally got a gigabyte with onboard video/hdmi/spdif ect and am happy with it.
So google the MB when you pick it out, thats all im gonna say, will save you a headache later.
And the short answer, YES! And go with XP x64 over vista, XP takes up a lot less resources, 1gb of ram compared to like 2gb for vista or 7 and thats with bare minimum OS stuff.