From what you've said. I'd go with a single 3.0 Ghz P4C with HT. I voted for what I considered your best bet though from the options listed.
With a HT P4C you can still do plenty of stuff at once efficiently since you said you enjoy that ability and since you play games 50% of the time it will be very fast in games as well.
You also have one of the best, most stable platforms under it as well the 865/875s. Incredibly cheap too for some of those motherboards. Especially if you're willing to use Newegg refurb like I would ($40).
I use a 1700+ on a Nforce 2.. not exactly a hot system but I'm a fan of both Intel/AMDs stuff. Nothing wrong with the P4C at all, and sounds like its right up your alley. If I was to buy today for myself, what I recommended would be my pick for myself as well.
I honestly prefer Intel though until socket 939 and the NF3-250 is on the streets. Thats what I'm waiting for. I wouldnt suggest you wait, 865 Intel stuff is incredibly cheap now. The price premium on Grantsdale with DDR2 and being new isnt something I'd recommend you wait for

Not worth it.
Tough to beat that tried and true Intel platform that has price, maturity, and probably overall stability on its side.
Sounds like your openminded enough to give it a shot as well!

Someone like you needs HT.