More Lumens=Higher Yield?

I have an 8x8x10 basement bathroom grow area where I've used 2 400 wt HPS lamps over the years with decent results (depending on the underlying genetics). This is a just the basics setup. I've never been too concerned with heat or smell and disperse the heat with a Vornado fan. I'm considering using only a 1000 wt HPS lamp in the hope that it might give me better yield and tighter nugs. Do they put out twice the heat to the point where I'd have to add something to cool the room down? More importantly, will I really see an improvement in yield? Is there a point where you can give the plants more lumens than they can use in photsynthesis? Thanks for your thoughts.

Chances are your two 400watt hps give out the same amount of heat probably more than a single 1000watt HPS lamp. Whats the cfm rating of your inline fan. Giving more lumens doesn't necessarily mean a higher yield. If you want to get a higher yield with your 2 400w hps lamps you can add more reflective material (preferably Mylar) to your walls and ceilings. Also try scrogging & longer veg and you can also try using more organic soil and better nutrient combination. The genetics on your seeds also can determine yield, theres strains that can do 100g/m^2 and strains that can do 300g/m^2 in the same conditions

I would go for 600w lights if you want to upgrade. They are the most efficient of the higher output hps systems as far as lumens per watt with only marginally more heat. They will fatten your buds nicely.

I will 2nd the suggestion for 600 watt lights.
an old rule of thumb for HPS is 50-100 watts per square foot. over 100 watts will see diminished returns- jumping from 100 watts to 180 will not give as big an increase as going for 50 to 75watts per sq ft.
you will see an improvement if your plants dont lack anything else. they need light,water,CO and food. increasing your light wont help if the nutes are not availible for the plants to use.