With 370HP in order to make a 7:51 it would have to be much lighter than the GT3 and with sportier more track oriented suspensions, chasis, differential, etc setup than a GT3
I doubt it will be either lighter nor better handling than a -20mm 997S (7:59) nor it will out handle the Murc and Gallardo by so much that it will compensate their 570HP and 500HP respectively since they both do 7:52 in the ring... so I doubt it would go sub 8min at the ring, not even with R-compunds by far.
Considering it will be a bit lighter than its bigger brothers thought it shares the same chasis with, around 370HP, and a sportier setup than the DB9/Vanquish though within Aston Martin's philosophy, I'd say around 8:15 tops with street tires will be more like it. Which would still be great since it not a track day car and its strongpoints are elsewere, sporty yet confortable, luxurious ambient inside, image of elegance and class, one of the most beautiful designs in the market, exclusive, etc.