I have a 40D and I like it.
I also use Sigma lenses and I like them.

I also visited your gallery, and liked it.

BUT: with the 70-300 you won't be able to make the macros you make now.

For things like that, you'd need a 1:1 lens like the Sigma 50, 105 or 150mm, all three f:2.8.

Gor wildlife at further distances, a larger tele is needed, but a 300, or 480 (multiply with 1.6) is as good as impossible to use handheld in real-life situations. So you'll need a tripod.

etc etc...

There are no Borg. All resistance is fertile.