4 speakers in a large room

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

@migueca Take a look at the current Yamaha integrateds (or any other similar design).  They have a few with different power ratings.   You can hook up 4 speakers to it (A, B or A+B).  FWIW, I have the 701, and just picked up the 501.  I use the 701 to power one set of speakers (A) under my eaves and the other set is being fired into the yard (B). Or, I can do A+B.  BTW, i have the Spektor 2s and they mate very nicely with the Yamahas.  Please report back with what you decide with impressions.  They're very helpful to others!

Does the A+B on the 701 use series wiring?

I've never tried A+B, but think my old Carver MXR130 may have that option.

DeKay

@dekay  Has it right.