In your situation I wouldn't use a mast mounted preamp. Instead, I'd opt for a Channel Master 4 port Distribution amp.
http://www.channelmasterstore.com/An..._p/cm-3414.htm
A preamp isn't advisable due to the presence of strong signals such as WMYA at over 70 db in signal strength. If you attempted to run a preamp in this situation, your likelyhood of signal overload is too high for my comfort level. Overload would manifest itself as degraded reception compared to without the amp.
A distribution amp is better suited for your situation in that it is only compensating for you the loss of your signal being split. I've used the analogy before, when a stream of water get splits 3 ways, without any additional water pressure it loses pressure and 3 new streams are less than the original unified stream. Signals work the same. The more you split them, the more you reduce the overall signal getting to the TVs. This is why when you start to get past two splits, some form of amplification may be wise to consider.
The way the chain would work is that you'd have your antenna... coax heading down from antenna.... coax into home.... coax into distribution amplifier.... each new coax goes to it's dedicated TV. The four port is nice in that it gives you one port to grow down the road if you want to another device to receive the signal.
Many times people split their antenna feeds 3 or 4 times and wonder why some signals aren't reliable on one or two TVs. Sometimes it's variance in tuners, many times though they can be found to be using a unamplified splitter and the signal within the coax on the weaker stations is falling below reception threshold. The distribution amp helps offset this.
Cheers.