Wonder who can provide good hardware for colo? I will need some low-end boxes like P3 with 256MB RAM, also high-end likes Dual Xeon or Opteron. One note is I am not in the US now, I know some providers require an US-based company
Dell and HP are some of the major companies you can purchase servers off of. Try to see if they have a presence in your country. You could also try knocking on the door of RackMountMicro and RackMountsEtc. Both run excellent operations as well.