If you already have a stereo amp to use stack them tweeter to tweeter (wired in series) and position them to cross towards the middle of the space (for starters).
Series wiring would be amplifier + to speaker 1 +, speaker 1- to speaker 2 +, speaker 2- to amplifier -.
You could try this with cheap speaker cable to see if they will properly fill the space when stacked.
Another trick to get more ambient/room filling sound would be to place them on very low stands or even the floor, but with the front tilted up a bit (you could try this with a single pair or a stacked pair).
Series wiring (your speakers are rated 6 ohms) would theoretically let the amp see 12 ohms, but realistically the load would probably be closer to 8 ohms.
Stacked 6 ohm speakers wired parallel would most likely drop well below 2 ohms - not a good thing.
DeKay