I haven't found antix distro for 64 bit systems. Is it possible to update base antiX-M8 distro to amd64 packages? Thanks for your help)

There is no antiX 64 bit distro, but antiX does work on 64 bit systems (as I am sure you know)

As far as I am aware it is not possible to update antiX-base to 64 bit.

On machines with Core 2 Quad processors and 8 gb of memory, how much of a performance disadvantage would it be?

I'd like all my machines running the same distro of linux (ie antix, sabayon, debian lenny, etc) and its difficult to find a distro that can run on my laptops because some of them have wireless and etherlink III cards for network access, which doesn't work on any other disto I've tried so far, at least not out of the box, and it looks like a herculean task to install the software on the others, if it were to work when done.

Congrats to antiX for being the first I found to work!