4ea. 3000k ab bin 3070's at 1400ma would rock your tent. The A51 really is not on the same level. (Apples and Oranges) .
2 of them will fit your budget. You won't be disappointed.
Let's do the math.
8 sqft X let's say 30w sqft= 240 watts \ 60 watts per cob at 1400ma=4 cxa3070's s so 4 will work, I'm with the cap'n 6 would be better, but you can fry them if you're not careful.
Call up Arrow and order a 20 pack of 3000k ab bin 3070's and Jamco for 1400ma meanwell drivers and New Egg for heat sinks.
I'm running 16 of them over 36 sq ft and it works very well.
Consider yourself spoon fed. ;-)
https://www.rollitup.org/t/diy-led-cree-cxa3070.789575/
It's kind'a long but this is the best that can be done right now easily.
Yup! This is exactly what I'm seeing going from Agro bulbs to 3070's Longer flower time and more stretch. The first harvest was up as well though had to go 5 extra days.