If the signal is usable at the set end for one TV (i.e., the desired channels are watchable without a preamp) but the 3+dB loss of 2-way splitting makes it unusable, then a simple low-power distribution amp might be the solution, with just enough gain at each tap to offset the splitting loss. More amplification also equals more noise, the bane of digital signals.
Any kind of amplification won't give you signals that aren't there, but if you already have usable signals with no splits you have a strong start and a baseline from which to assess any changes you make. If you're also trying to receive channels you don't get now on 1 set using preamplification (agreed, that's the best method), that's a whole different story.
Try the split first without any amplification and work from there. I happen to be using a 4228/7777 combination. I took some tinkering to get that to work at all. In retrospect I might have been better off with no or less preamplification, but I never tried those options. When I finally got the a/m combination working reasonably well on one set, the 2-way split to 2 sets seems to work equally as well...