Hard Drive Swapping between Dashes

I haven't seen an exact answer to my questions yet. so i figured i would ask.

- I’ve got a un-banned 360 with LT1.2 on the old dash that i took offline before the update. Ive been waiting for LT+ before putting it back on.

- I also have a brand new untouched Xbox, even still in the box. Never even been opened.

I’m really getting itchy to pick up Kinect, but I don't really want to update that one Xbox yet. What would you think would be the best situation for me to do?

Thought about running both and swapping HD's back and forth like during the last ban wave, but I heard it will update the old dash ether way. Or I’ve thought about running both and putting my Profile a USB key and swapping that hoping it won't update. Even if I decide to not get Kinect just yet I would still like to update my offline achievements. That’s probably more important to me anyway. Anybody run into this situation?