I may have to use Tony's Sigmonster a bit... I think we may all have to!
Hopefully it gets another good use at this weekends D1NZ on Sunday, however don't know if I can get the day off work yet!
I'm definately buying a 1DMkIII, and in about 2 years when I'm completely debt free, I may consider a 300-800mm, for wildlife photography and other stuff. For now, the 120-300 is perfect, and I may buy the 2x converter within a few months, to try 600mm F5.6 to see how sharp she really is.. you never know, I may not need longer than 300mm 2.8.
400mm 2.8 is so heavy and expensive, may as well spend the same on a 300-800 with more use. The Sigma 500 4.5 doesnt seem to exist. Maybe Sigma stopped making it.
So my likely future in photography, (providing I stay free lance, or not employed by somewhere where I get free equipment),
1DMkIII
1x 580EX
1x Macro lens
Keep the 20D as the 2nd body
I think then, I could keep all the lens for approx 5-10 years, and bodies replace every 3 years, give away the 20D to family, it won't be worth too much, maybe $700. ANd buy a 1DSMkIV. 
Oh, and I've decided I'll buy a Mini Cooper S, black or blue and have it signwritten with my details
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That car is hot...
Oh let's not forget the future.. House, wife, 7 kids... Better get the camera gear before it's a firm NO.
