i'm an installer for comcast...lemme shed some light on things
for signal amps, you MUS make sure they're bi-directional. uni-directional amps will boost the signal to the modem or tv, but block the return and wont let your modem work at all
if you're gonna split the cable, go to home depot and get the Ideal brand 1GHz splitters, DO NOT USE CHEAP RADIOSHACK/RCA 900 or 600 MHz splitters. You'll also want to use RG6 cable if you're spitting, RG59 has a tendancy oof losing alot of signal after the split. also i've seen so many ppl try to do their own home wiring so sh*tty and they cant get it to work. SO they call us out, and we get there and its a frigging mess. So if you dont know what you're doing, dont even attempt trying, you're just gonna end up calling the cable company.