> I could use x64 kernel with x32 system?
Yes.
> How to use that?
Just "aptitude install linux-image-2.6.32-5-amd64".
Such "32bit userland on top of a 64bit kernel" used to suffer from
corner-case bugs (like wpa_supplicant or s2ram not working) when I first
tried it (like 5 years ago), but nowadays it seems to work perfectly
fine (it's what I use on pretty much all my machines).
Stefan