Phono Stages with External Power Supplies...Worth It?

Get the $1200 version if funds are a little tight. Apparently, you can upgrade for the extra $700 without penalty down the road. However, you may regret not extending the card initially. Generally, a beefier PS brings small improvements in stage, tighter bass, increased dynamics and lower noise floor.
There is one for sale here for $800 obo which you could upgrade and save some $.

Can't say about the Odyessey power supply but I've ordered the $900 Gold Note PSU for the $1250 PH10 phono unit. Is it worth it? Several users say yes, hope I find it the case myself.

You've asked an impossible question.  To answer it intelligently, one would need to know much more about the differences in the power supplies between the version with the external box and the version with the on-board PS.  Can you do some research and give us more to chew on?  It's true that a large fraction of the premium you will have to pay to get the outboard PS is due to the mere fact that you are getting an extra chassis.  However, regardless of all else, having the external PS usually leads to lower noise. But if the base unit is already "quiet", maybe the extra cost is not merited.  

From what I have read in the Odyssey Forum on The Audio Circle, it is a very worthwhile and noticeable improvement.