Snow Leopard and audio quality

I'm reviving this thread because sidssp asked an important question about 64 bit kernel operation that was never answered.

When you boot up Snow Leopard, it normally boots into 32 bit kernel mode. You can confirm this by going into "About this Mac" then "More Information." Highlight "Software" in the left column. In the right column, it will say, "64-bit Kernel and Extensions" and probably "No." To boot into 64 bit kernel, just hold down the 6 and the 4 key while it's booting up (Once you see the apple, you're fine.) To confirm that you're in 64-bit, the "no" should have changed to a "Yes."

If you have a resolving system, the improvement will be evident. I find that the sound is more relaxed, natural and open.

So if I do a clean install of Snow Leopard I have to back up everything in the computer. When I download all the stuff back into the computer after installing Snow Leopard, what happens to my OSX 10.5.8? Does it go back in as well and then needs to be deleted or how does that work? I don't see where you can isolate all programs in the Mac. It is either take everything out and then put everything back in or nothing. Is that right?

Let me rephrase my question better: Do I remove everything from my iMac including the operating system? I am only using 17.1 GB on the Mac HD currently which must include the OS. So if I remove everything, will Snow Leopard (10.6.8 ?) take care of removing the old OSX 10.5.8 when I reload all my programs back into the iMac?

Next step after that would be, I presume, to download all the upgrades to Snow Leopard in case I get the silly notion to upgrade again to Lion.

I know it is bad manners to respond to your own post but I want to be sure a reader understands my question.