Please dont do the use and return route. Uber uber tacky.

You can use a computer monitor with dvi input and a dvi to hdmi cord in a pinch to your AVR. They are handy to have and cheap to buy.

I cant remember what AVR you are using, but usually speakers are set to small (or sat+sub sometimes) and crossed over at 60-80hz.

One sub behaves well at 1/3 points along front wall as a rule. Sub should have gain at 12 O'clock to start.

I wouldn't judge anything until you get your AVR setup correctly.