Hi Homebrew, technically i cant really give you a solid answer on whether or not im pulling a lb per fixture. i will try and explain what my grow is like and you can make up your own mind.
this is one of my current rooms, its a small scrog 1 foot x 3 foot. it is powered by a single 400w CMH and is just starting to flower.
i pull 6-10 oz from this small space consistently and i honestly think if i doubled the screen i could come close to a lb from just the one 400w CMH although thats only an estimate. completely unproven so please dont quote me on that but i believe it is doable.
now moving onto the dual 400w space and you will see its quite a beast and yes i can pull pounds form this area with ease. i could pull even more if i spent more time on canopy control etc. (might be worth mentioning here i use no bloom boosters etc. simply base nutes and bennies throughout the whole grow so what you see here is au naturale yield wise)
^^^^ at around 5-6 weeks. after this they started falling all over each other so i stopped taking full room shots lol. the rest of the shots are around 8 weeks
^^^^ you can see in this pic that the penetration to lower bud sites is quite good
the dual 400's yield as well as my 1000w
solistek ballast running
solistek digital HPS lamps. Only the quality on the CMH 400 combo is better IMO better plant health over all. i dont know if its because of the light spectrum or just its easier to keep the plants from getting heat and light stress under the dual 400's compared to the 1000w but i know they work well for me.
as for the new lamp the 315w i havnt got mine yet but a friend of mine has done some testing with his own light meters etc and the results are very promising, i cant quote the figures simply because i cant remember them all of them off the top of my head. he is suggesting though that its around the equivalant in PAR to a 600w HPS.
i plan on building a whole new space for the 315w. it will be a 1m x 1m space and i will scrog a clone im familiar with and see how it goes in there. if it can turn a decent yield in a 1m x 1m space on its own i will be very impressed and i will probably get a second one and double them up in there.
sorry about the long winded reply, i hope i actually answered your question somewhere in there lol