I am creating an apex generated chatter post to put big deals into a big deals group.  I want to put information about the deal including the amount.  I am having issues trying to get the amount to display in its currency format.  I am pushing it to a group so chatter free users can see it too.

trigger PostBigDeal on Opportunity (before update) {
    
    //vairables for use later
    List<Opportunity> OppIds = new List<Opportunity>();
    List<FeedItem> feeds = new list<FeedItem>();
            
    for( opportunity opp: Trigger.New){
        	
        if ((opp.Big_Deal_Post__c == true) && (trigger.oldMap.get(opp.id).Big_Deal_Post__c == false )){    
            oppIds.add(opp);
	        }
        }
    
    if (oppIds.size() != 0) {
        
        for( opportunity BigOpp: [SELECT Id, owner.name, Subscription_Type__c, amount FROM opportunity WHERE Id IN :OppIds]){
   
            FeedItem post = new FeedItem();
            post.ParentId = '0F9Q00000004SiM'; //eg. Opportunity id, custom object id..
            post.Body = 'A New ' + BigOpp.Subscription_Type__c + ' has been sold for ' + BigOpp.amount + '.  Congratulation to ' + BigOpp.Owner.Name + ' for their hard work!';
            post.LinkUrl = 'https://cs3.salesforce.com/' + BigOpp.Id;
            feeds.add(post);
        }
        if (feeds.size() > 0) {
        Database.insert(feeds,false); //notice the false value. This will allow some to fail if Chatter isn't available on that object
    }
    }    
}