Hiya Michael,
I am unaware of any "stand alone" gateways that are available at this time. I do believe that at one time they did do some gateways separately as extensions for the Shopping Cart programs, but these have since all been incorporated into the programs themselves which include PayPal as well as a few others like those you mentioned.
There will also be some incorporated into the HTML Web Form Builder soon too. I don't believe CC does "stand alone" versions of these gateways any longer.
P.S. CC if I'm wrong please let me know, but I am pretty sure that's what I read in an email a quite a while back, like a couple years ago already.