I have an all-male peacock tank. They get a little feisty around feeding time, but it's not a battle royal at all like when breeding is involved. I'm a big fan of the bachelor pad.
Try and get Peacocks with different adult color schemes and patterns. Also try and get them all at the same time and at roughly the same size; they'll grow up together, which will minimize aggression somewhat. Feed them plenty of color-enhancing food, along with some plankton/krill and spirulina once in a while (Peacocks don't need the spirulina really, but mine respond well to the change of pace). One or two males will rise to dominance (and full color), but your big tank will help minimize any serious hassles. The Jacobfreibergi, based on size and temperament, might assert itself as the top Peacock.
Try and strike a good balance between rocks/caves and plenty of open water. I also recommend a sand substrate (pool filter sand works fine - just wash it well before it goes in).
As far as fishload, you can probably get away with 12-14 adult fish if you keep up the 20% water changes every 10-14 days. Get excellent filtration - perhaps 2 powerfilters and a canister. That Frontosa will get big!
One final thought is you might want to throw in some different fish for variety's sake. Fortunately, 125 gal is pretty good size tank that will let you experiment and branch out in terms of selection. I might recommend a mix of the following:
Peacocks
Borleyi (or other Copadichromis)
Labidochromis
Julidochromis (only keep 1)
Electric Blues
A. Calvus or Compressiceps (only keep 1)
Brichardi Daffodil (only keep 1)
Tretocephalus (only keep 1)
Leleupi (only keep 1)
Synodontis cat
Even if you're fairly sure you have a bachelor tank (if that's what you want), still keep a sharp lookout in the early stages for weird breeding activity. Four male peacocks and an accidental female mixed in could get a little crazy.
Good Luck.
