The modem status info you provided, while it looks good (-1 dBmV downstream power level, 37 dB SNR), it only applies to the relatively small band of frequences allocated (usually in the 500 to 700 MHz range) to handle the cable modem downstreams. The TV channel(s) that has the problem could be hundreds of MHz away from there.
It would be more useful for you to get the signal status info on the particular QAM carrier(s) that carry that TV channel(s).
See this post of mine in another thread about that: »Re: [HD] Fox Ohio Valley College Football Broadcast
Going by the modem status you posted, you will likely not need to use an amp, but instead, to just fix a cabling/connecter(s)/splitter(s) issue.
If the problem is not inside your home, you would then need a tech visit to investigate an outside issue.