The Digital Tv stations/channels are Very Strong at your location.
For a attic installation of a Tv antenna install a Antennas Direct Clear Stream 2 Complete UHF/VHF antenna ,
http://www.antennasdirect.com/store/...VHF-Combo.html.
Remove the Reflector Screen from the CS2 Complete antenna and the CS2 Complete will receive at the front of the antenna and back of the antenna.
The 2 groups of Tv stations are to the west and east.
With the reflector screen removed aim one side of the CS2 Complete at 80 degree magnetic compass direction and the other side of the CS2 Complete at 260 degree magnetic compass direction.
The coax cables and splitters and etc. that are in or on the house that are used for the antenna system Can Not be connected to a coax that has Any Type Or Kind of active FIOS service.
If the attic is wood with standard composition shingles and no metal backed insulation and no metal roof and no thick roof tiles , reception should be fine.
No preamplifier or distribution amplifier should be required.
Try the CS2 Complete antenna connected to the current splitter set up , the signals are so strong it will most likely work Ok.