Slot1: this is about the easiest to seal up for peltiers, but it's harder to find copper waterblocks for.
Slocket Adapter: Any ole Socket waterblock will fit it, requires a lot of work to seal for peltiers, but you don't void your motherboard warrantee sealing up a slocket.
Socket370: Any ole Socket waterblock will fit it, requires a lot of work to seal for peltiers, sealing the socket up will void the motherboards warrantee.
For plan water-cooling, Socket370 would be best. For water/peltiers Slot1 would be the best, with slockets coming in for a close second.