The Anderson connectors are the best way to go. These are readily available at NAPA style auto suppliers and Home Depot Stores. Keep it simple.
Also, the connector the OP noted, will not serve you well because you are limiting the electrical transwer for the size of the connector. Just like have the correct guage of cable, your connectors need to be upsized as well. Why do the upgrade if you own work/supplies are going to negate much what you want to gain in power. Don't cut corners here in cable size, connector size and what has not been talk about yet, distance between the two batteries that are being hooked together. You would be better served to have the batteries closer together, if not end to end or side by side.
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