"Dlaude", that PCT amp I got is still working fine. I don't know much about the EVO amps, but many cable co's use PCT. You need to compare the detail specs (THD, noise, S/N ratio, etc.), between the two to see which may be better. At the PCT site (which I probably linked to in my prior posts), they have detailed PDF files. The PCT is also cheaper.
If the existing box still works fine without the splitter, and you're sure it's not the cables, then it's obviously a low signal.
You need to put an amp where the cable comes into your house.
For some reason I have two main cable lines incoming and I only amplified one, the "main" main one. The other goes to the kitchen and outdoor area, I recently put a TV in the kitchen and it can't pick up HD cable channels very well (breaks up) so I have to get another amp. I'll either get another PCT, or I just saw this I need to look into: http://www.mcmelectronics.com/product/30-2400
($12.99 w/code A20812 and you can probably find free shipping codes). I don't know the significance of "return-path amplification", see the review.