Next Purchase, what would you do?

Im looking to invest in another piece of camera gear

Here is what I have now

40D with Grip
Canon 50mm 1.4 USM EF
Canon 180mm Macro L 3.5
Canon 420EX flash

I have approximately $1000 to invest in something.. likely used.

I tend to shoot, my Kids, local nature (birds), Macro Bugs and Flowers, Go to Zoo often , Landscape HDR, Candids

I was thinking of getting something with more reach, hence the 400 listed below.. but i considered possibly just adding a 2x to my 180macro which is very sharp.

Some ideas I've had.

Canon EF 400 F5.6 USM - for birding and zoo trips

Canon EF 135 F2 - Kids and Portraits

Canon 17-35 F2.8 USM - Wider for family or landscape

580ex II Flash

2X Mark III Multipler

5D Mark I

What would you do?

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View my gallery here http://www.filipowicz.ca
Canon 40D
Canon EF 180mm F3.5L USM Macro
Canon EF 50mm 1.4