Is it permissible to take two gold rings home to get the wife's opinion, with the seller's approval, knowing that the payment will be made later?

Selling gold with the option of return (khiyar al-shart) is not permissible because it constitutes usury (riba), due to the lack of immediate exchange (taqabud) in the same session. As for handing the two rings to your wife for the purpose of viewing and consultation, if the transaction is then concluded with immediate exchange in the same session, there is no harm in that.