Your tank is small enough...I would go with the hang on. Then if you like Salt think of going with a tank that has a sump. I have 3 dogs and a cat hair is no biggy.

Yup sumpless, make sure you have as much rock as you can fit into the tank. the rock will make the sump un nessecary. rely on your power heads and skimmer to do the work. make sure you buy the very best skimmer you can afford. the pumps and lights should provide you with ample heat to keep it warm. im marine more cycled rock makes you more stable. always keep this fact in mind and youll be fine. I might get flamed for this but probably imo the best Hob skimmer is the little one made by instant ocean. that little guy hooked to a maxi 1200 really does a good job on the smaller systems.

I have minimal rock + sand in my 77 gal ~ 2 Power heads and a Aqua C Pro hang on skimmer and 7 fish.

hmmm minimal rock? how are you making that work with 7 fish?

It just does

I've got 55 lbs of cycled live rock and a good 3 inches of live sand but I have been thinking about putting more rock in my 20 gallon QT tank because it looks so overcrowded.

With the corner bowfront, there are only so many ways you can build the rock up and around because visibility is so high. Great for display, not so much for hiding places.

So then, if I get rid of my filter what happens with the spray bar. Can the output of the skimmer be retrofitted?

on the output of the skimmer you could retrofit it. make sure you arent restricting the output of the skimmer though, as it may reduce the effectiveness of your skimmer.

Yeah, I worry about that because skimmers can be so damn finicky and adding another variable to tweaking it might be too much. Has anyone had success in retrofitting the output on their skimmer?

You could also go skimmerless as well as sumpless

:shocked!: How? Isn't that sacrosanct?!?