All above are sound suggestions and observations.
It sounds like performance is a priority. Same with me. If so, 64-bit is not necessary. Neither is a DE any 'heavier' than LXDE. This narrows it down a bit (looking for a distro with just a WM or lxde . . . hmmm).
You may also want to look into antiX
However, like CrunchBang 'Statler,' it is a Debian distro and Debian is in transition, waiting for Wheezy to go 'stable,' and sid-based distros are for adventuresome hoppers, so . . .
Slackware-based distros come to mind. But Salix-lxde is still at 13.37, leaving but ones like Slackel-openbox
which is pretty impressive, using Slackware, Salix and its own repos. Openbox WM is very responsive. A little Greek pops up in the menu at right-click occassionally, but international symbols and its place on the menu window makes selection of no real concern, if a bit disconcerting at first. It is available at Sourceforge here.
Once again, snowpine and I are of like mind. 12.04.1 fom Italy with e17 is unofficial but very well done is Salent OS.