any sativa should be ok if you dont get too wasted on it...
but really the only thing that will get you motivated to do stuff is yourself, if you cant ge off your ass to do stuff then i doubt any weed would really help.
personally i prefer to get the stuff i need to all done, and then get righteously stoned afterwards
I will second the recommendation for an early harverst or rather the warning not to harvest late if you like motivational high.
As for a strain, since you want motivation with yield, which is quite a common dream , you have so many haze hybrids and phenotypes to taste and choose from
Durban is the speediest of all weed I've tried, with a serious and focused high, wonderful for doing work (the strongest high you can get and still be functional!!), but lacks positivity.
The clearest high I've tried is from an Eldorado pheno of Nirvana's Royal Flush (good yield for the quality!). So clear, that a little will make you feel perfectly normal but happier and with more energy. But it depends on how clear you really want to get, because some friends who enjoy heavy hitting highs, say it gets them "on the edge of getting high"
Not from experience but my good freind swears by JEDI. He says he's like the jedi warrior of getting shit done when he smokes it. He said "I smoked a bowl and I just reeeaaaally wanted to clean my room".
I'm glad you said that. There is strain called Boba Fett Haze. It's a small breeder I believe. It definitely has some Jedi in it, as well as Neville's Haze I believe. Have no idea where to acquire the genetics, but man, this was the most energetic herb I have ever had the pleasure of coming in contact with. Held onto the tiniest amount for months, reserving it strictly for work in the garden. I would take a one hit and spend 4 or 5 hours doing shit that I had been procrastinating on for months.