You have a giant cube.. I'd recommend a lot of diffusion and corner treatment if you can get away with it.
Anything is better than nothing. I've been in many rooms exactly like that. It is tough to tame.
Absorptive panels are fine in specific locations but you'll end up hearing a lot of reflectivity behind you in that setup. It's got to be balanced out... I'd try spreading the panels out to hear how that changes things first. Consider a floor standing panel to separate the kitchen.. even something small (like a 2'x4') behind your head might work.
Without diffusion you will essentially need to cover that entire room with panels. Start reading up on diffusion. If you get the diffusion right you can use some of the panels you have as bass traps.
Another option is to hire an acoustic designer to come in.. like Rives or someone like that. They'll give you the exact answer (at a fee of course).. but just throwing out some ideas.
-C
