Macbook Pro Tools and an External drive

[spanktastic]

Hello
I am looking to upgrade my studio to Mac to improve efficiency
I will be using M Powered and Firewire Interface
I would like to be able to use a Macbook with 2.4 Ghz and 4Gb RAM
the problem is that they only come with 5400 RPM Drives
I need 7200

Would an external drive be okay?
Would a Macbook with 2.1 Ghz be alright?
Will Pro Tools run from the external 7200 or transfer after start up to the internal 5400 or how do the drive speeds effect Pro Tools?
Should I get a USB drive since my firewire would be taken up?
Any External Drive Recommendations?
Also is Pro Tools M Powered 7.4 Mac Leopard compatible I wanna run it with a Profire 2626?
Should I just upgrade to Macbook Pro?

Can anyone take on the challenge to help me? 8D