You might want to look at the cost of having a coaxial antenna cable installed into your server room. In Australia the installation of an extra antenna outlet point cost around AU$60 when done at installation time. A little more, around AU$105, if done later on. That may be cheaper than buying a network tuner and setting it up out with your HTPC.
With a good antenna and professional splitter installed on the antenna line in, you should still get a strong enough signal for the tuner. I have an unpowered three way splitter that works fine, and it only cost about AU$15 from the installer. I did need to get a new Digital antenna when I installed the quad tuner into my HTPC, but that was because my old antenna was analogue, and from the early 1970's! Don't do the installation yourself though, as a professional antenna installer can test the signal strength and advise if a powered splitter is required. Also if you can, look up the signal strength required by your tuner and let the installer know. My quad tuner required quite a strong signal for all four tuners to work well.
It sounds like your server room is set up so well, it would be a shame to have to have the network tuner out with the HTPC, in the heat, cold, open etc.