now i have been running mono amps for a while, and some have 1 speaker output and some have 2.... why??? like my T10001BD had 2, but my swiss audio SDX2000D had one... i dont understand ????

Ease of wiring. Like if you had two subs and you want to wire them down to 1 ohm and there is two outputs out of your box, you can put one to each terminal instead of cramming them into one terminal. The two terminals are connected inside of them amp.

alright, so what if i only have one sub which +and - should i hook it up to? or does it depend on the amp?

Doesnt matter they are connected inside.

one output ..... 4 screws.

Choose a set and be done with it. It's really that simple

alright, so what if i only have one sub which +and - should i hook it up to? or does it depend on the amp?

Use the most distant ones. In the event a strand of wire is left out there's a smaller risk of shorting out the output.