[ZPaul]

Internet speed is determined by the slowest part of the path.
Connection to the house is the responsibility of the Internet Service Provider(ISP).
Modem at that point can limit speed. Having dealt with Comcast, rental modems are not generally replaced when newer, better ones come out. Being technically oriented, I buy my own.
From modem signal travels by wired connection to WIFI router or direct wired connection.
WIFI speeds depend on the speed of your router AND the speed of the WIFI built into the end devices.
WIFI routers should be located high and in a location where penetration through walls is nearly straight on. Signal is straight line meaning, the more wall/Ceiling material passed through, the more degraded(slower) the signal.
WIFI routers with multiple visible antennas provide stronger signals than those with "built in" antennas.
Most modern routers offer multiple bands. If you use the lower 2.2GHz band, you generally are very limited in top speed regardless of the speed provided by your ISP. The drawback of the higher frequency bands(5GHz etc) is that they degrade more with distance and wall penetration.
To get true 1GHz speeds, devices must use the high frequency bands.
If your devices can not run on these bands, then buying 1GHz from the ISP is a waste of money since you can not achieve those speeds through the low frequency WIFI band. This is primarily a problem for older devices.

Finally, running physical wires has its drawbacks. Like everything else in computers, wiring becomes obsolete with time. Old wiring in walls becomes slower than an up to date wireless connection. Other than manufactured housing areas, running new wiring in Villages homes is difficult. If building new, make sure wiring is to the latest, more expensive standard(Cat 6 currently) as it will take longer to become obsolete. Once it is obsolete, you need to either run a dedicated wire for your wireless router or put your router in the garage near the ISP incoming modem(not ideal from for wireless signal strength in house).