Help Upgrading from Pro Tools M-Powered

[thglif52]

Hello everyone,
I'm a long time home Pro Tools user and I was just hoping to get people's opinions on which way to go with a current upgrade situation.

I am currently running Pro Tools 8 M-Powered and just bought a new 27" Imac which will be running Lion OSX so I will have to upgrade to a newer version of Pro Tools. I was hoping to not break the bank and upgrade to either Pro Tools 9MP or just the regular Pro Tools 9. $500 seems like a ton of money to spend after just buying a new computer. The upgrade to MP9 is $199.00 on the Avid site and I've found some crossgrade options to the regular version of Pro Tools 9 for around $350.00 on other sites.

I was just hoping somebody had some opinions on the best way to go. I do have two M-Audio interfaces but thought it would be nice to be able to free the software from the interface if need be for occasional mixing. Thanks for any input.