I would say go for 2 or 3 standard chickens plus your two silkies (they really are adorable). These would fit well in your existing run, provide you with more eggs than you need, and also allow you room to add to your flock in the coming years. You may want to do this down the road because:
a) baby chicks are cute
b) you're going to get excited about different breeds and decide you want/need them
c) younger hens lay more eggs than older hens, and you might not want to get rid of your birds that are past their egg-laying prime
If you do decide you want 10 birds, then to meet the 10 square feet rule you should add roughly 4' on to one end of your 8'x8' run (ie. make it 8'x12', 8'x13' or greater).
Good luck!
a) baby chicks are cute
b) you're going to get excited about different breeds and decide you want/need them
c) younger hens lay more eggs than older hens, and you might not want to get rid of your birds that are past their egg-laying prime
If you do decide you want 10 birds, then to meet the 10 square feet rule you should add roughly 4' on to one end of your 8'x8' run (ie. make it 8'x12', 8'x13' or greater).
Good luck!