Wachovia Corp. officially bought AmNet Mortgage this week for $83 million in cash. The companies announced the deal in September. AmNet’s shareholders approved the merger Dec. 8. Many industry watchers see Wachovia’s purchase of AmNet as just another indication that lenders will use the looming down cycle to go on a merger spree in order to compete better with the large lenders such as Countrywide and Wells Fargo. …