Canon EOS 40D and Nikon D80 and Sony a700and others

You like Canon then buy Canon law...
Normally when compare 40D /w D80 , 40D is better, but 40D compare /w D300, D300 is beter, compare /w their function, white balance, iso, focus point, ...etc...

if you love Canon style and brand name, you should buy 40D.
now the street price is around $11000 /w 17-85mm len,
400D is much cheaper abt $5480 /w kit,

buy 400D or 40D depends on your need, how lond will u use, you need 6.5 /per sec, DigiIII processor, ...etc...

so I suggest, for a beginner /w limited $$, 400D is OK , so that you can use $10000 buy 2-3 better lens [ L grade lens] , if you buy 40D kit you can only buy 1 L grade lens.

Normally, Sigma lens is similar to Canon normal lens [not L lens] ,
sometime sigma lens clr is better, sometime canon usm is faster or more stable,

so in my opinion, Canon "L" lens /w canon DSLR is better choose for you,
why people buy sigma lens, becoz sigma is much cheaper and some lens canon don't have that range ...etc..

so If I was you, i will buy 400D body /w 24-105 L and 70-200 L lens.