Need some more specifics like what filter are you running, how planted is the tank and what do you mean by "cave"? Would you happen to have a picture of your setup? With well planted tanks, you can generally get away with a slight overstock but you;ll always get the people that will chime in and tell you that you're cruel for keeping a smaller tank overstocked.
Your current stock seems fine for that tank but your new stock would put you over the general "1 inch per gallong" rule. Like I said, depending on the amount of plants and equipment on the tank, you could get away with it just be prepared for any issues that may arise.