Some general information.
A full sized purpose built antenna is will usually give the best performance whether it is a 3 element or 10 element antenna.
How much of an antenna will be needed will vary location to location. What works well for one person may not work all the well for someone else in a different location, even within the same town or sometimes even with in a few city blocks. It depends on how much signal is
hitting the antenna.
I have read a number of positive reviews of the
Stellar Labs antenna. It is a basic 4 element FM broadcast band antenna and it is not rocket science to get this correct. However the same caveat applies. I understand that this may not fit you definition of a big antenna and may not be enough gain for your particular situation.
To be clear, when you say that you all ready have a distributions system, does that mean that you also already have an over the air TV antenna? My take is that you do not, but that may not be correct.
Using an over the air TV antenna for the FM broadcast band can be hit and miss, trial and error. Not all over the air TV antennas are created equal when it comes to FM broadcast band reception. If a combination antenna is to be used, are all of your stations of interest in the same direction from your house? If not a rotor may be in your future.
Using an FM broadcast band only antenna for over the air TV reception can be an even bigger hit and miss situation.
Check you existing distribution amplifier to be sure that it does not have an FM broadcast band trap, if it does be sure that it is turned off. Not all do, but it is not unusual, and some may have unswitchable FM traps.
It all boils down to how much signal is in the air, from what directions, for the stations of interest right where the antenna is located.
Eickmewg beat me to the reference to the Stellar Labs antenna.