Re: 64Bit and more memory.
I am so far from being a LOgic Studio expert, maybe I shouldn't answer you on this, but I am a computer savvy ex-network admin with years of Intel PC and Server experience. You probably already know you don't need 8 gig of memory to run Logic in 64bit mode, so you can experience some of what I am going to tell you without buying a thing. I did and the outcomes left me thinking it had to be the lack of memory that must of caused be problems.
I installed an additional 2 sticks of 1066 DDR3 thinking this would smooth out Logic's funny hiccups, but now I have a blazingly fast 32 bit Logic Studio 9.
I noticed first Logic reconfiguring itself to adjust to using 32bit au's etc., in 64bit mode, just like it did when my new i7 2.88 2TB with 4GB Logic was switched to 64bit. I just jumped from Windows 7 64bit and it seems to have many more vendors on board with with them.
Once configured, I felt like Logic was sort of blinking now and then like someone with eye tick. This annoying blip and the more annoying fact that most of the rest of my Logic 9 innards were still firing off in 32bit, just pissed me off. Logic just seems to feel smoother in 32bit, but I will admit a faster and smoother Logic Studio 9 with 8GB, then 4GB.