iOS Buy another device, just for developing for OS 4.0?

I currently develop/test on my iPhone 3gs, and my wife's original iPhone.

I'd like to develop for OS 4.0, but don't want to install it on my phone because I'd still like to be able to test on OS 3.

So I guess now I need to buy a current iPod Touch and install OS 4.0 on it, so that I can start developing for that?

Anybody else in the same boat?

I need to get an iPad as well... this is getting expensive.

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You're right... It's tax deductible, and definitely a worthy investment. Just not one I was expecting right now.

I'll gladly do it though... iPhone OS 4.0 looks very impressive, and I'd like to be prepared for its official release.