Connector Suggestion for Extruder and Heatbed
You might be able to use one of the connectors (Deans Ultra, EC3, XT-60/30, Bullet) that are normally used for RC models. They're made for very high currents. The XT60 connectors depicted below are rated for 60A continuous (well above what you'd need for any heated bed); their smaller XT30 cousins are good for 30A but less commonly available.


(Photo by Mark Fickett)

For your extruder you wouldn't need anything quite as drastic as an XT60, even a simple JST connector would suffice (though if you are going to source XT60/30's for your heated bed anyway, you might use them here as well).


(Wikimedia Commons, Mike Mahoney)