Apple Logic Pro /LogicExpress Discussion

Hi everyone,

I have a rather silly question.
I would like to upgrade to Logic 7.1 Pro.
I have Logic Platinum 6.4.3 now.
Is it possibble to upgrade to 7.1 and upgrade 6.4.3 platinum to 6.4.3 Pro?
In other words, if I upgrade to Logic 7.1 Platinum will I be entitled to use 
a copy of 6.4.3 platinum as well?
The reason why I am asking is the performance issues.
I knkow Logic 7.1 works better with G5 processors.
However, I have a Mac Mini and I have a powerbook G4 1Ghz.
I am not planning (can not afford to) upgrade in the next year either.

So, has anybody ever done this?
Any ideas?

Yavuz