If the signal from KGO, (broadcast on VHF CH-7) is strong and stable, I suspect the old antenna is a VHF only design. Unless it's damaged it would be useful and could continue in service, receiving VHF signals.
A UHF antenna is needed to reliably receive the majority of the available signals. Any of the 4-bay panel antennas would be a good choice. (U4000, DB-4, CS4, DB4e, CM4221 and HD4400) I would aim toward the NE (Sutro Tower)
http://www.antennacraft.net/index.html
http://www.antennasdirect.com/
http://www.channelmaster.com/default.asp
http://www.winegarddirect.com/
You would need a
UVSJ to combine the signals from the VHF antenna with the UHF.
Connecting a few tuners should not require any amplifier.
If it turns out that your attic is a poor location for an antenna, (wet roofing attenuates and reflects more than dry, tile and metal are also unfriendly to TV & radio signals). A small RCA ANT-751 mounted outside would be an option. It has both UHF and VHF capability.