Thanks Mark, yeah, I'm still learning this thing. I thought that it would be more taxing on the processing side. I'll check that out, test it.
It is a bit more taxing in the sense that Logic Pro will take up more of your system's memory. But I don't think all that much.
To be honest, I doubt you'll see any benefit from running Logic in 64-bit. I'm guessing that if you're in a learning phase, you're not using a ton of plug-ins, and you don't have any very large sample libraries. Also, with 6GB of RAM, you really don't have that much "headroom" to take advantage of.
For example, lets say you were a professional soundtrack composer with a Mac Pro loaded with 16GB of RAM and a number of huge ($1000+) orchestral libraries. Figure that Mac OS X will utilize about 1GB of RAM.
If you were using the 32-bit version of Logic Pro 9.1.1, Logic could only access 4GB of memory. So a total of 11GB of memory in your Mac Pro could not be accessed by Logic. This extra ram will be available to other applications running simultaneously, such as Safari, Mail, and so on, but not Logic.
If you were using the 64-bit version of Logic Pro 9.1.1, Logic could access 15GB of RAM, which is a huge bonus.
However, with your current 6GB system, even with the 64-bit version, you could only access 5GB of RAM vs. 4GB. That's a little bit of an advantage, but not that much.
So give 64-bit a try to see how you like it, and I'm guessing you'll find it nearly identical.
Orren