I have always put my kids down around 6-630 knowing that more sleep actually helps them sleep longer... I would get resistance from others that would tell me it was too early, but you seem to know as well as I do that keeping them up later isn't the key! Only makes them more fussy and sleep is all over the place.
However I will say this.... My now 21 month old was just ready to stay up a bit later and I had to accept that :)
She would go down at 630 sharp from around 5 months on! But I started to see right around 17 months that she was REALLY awake at 630pm (more than normal) and wasn't sleeping in like she used to. She would play in her crib until nearly 8pm and then finally give in to sleep. So we now put her down at 8 and she is back to sleeping until 7 or later.
While I am like you and believe a early bed time is key we have to be flexible that our kids are getting older and can stay up a bit later.
My now 5 month old is on a 6pm sharp schedule and it is great, but I will watch for clues as to when she is ready to extend that bedtime schedule a bit down the road.
Perhaps just give it a few day of putting him to bed around 730 and see if you get a later wake up call :) Its worth a shot...