Is it possible to use distcc on both an x86 and x86_64 machine to distribute the compiling for both machines? Or will compiling 32-bit code on the 64-bit machine result in invalid binaries and vice versa?
In theory it should be possible, I haven't been able to get it running myself though, although I must admit my attempts have been sort of half-baked. Have a look at http://dev.gentoo.org/~vapier/CROSS-COMPILE-HOWTO and let us know if you get it working.
The new crossdev in portage appears to work better than the previous version, so try that first. Using a nocxx flag oncross-x86_64-pc-linux-gnu/gcc is probably needed on the x86 machines.