Have you?
1. Checked the convergence on the toshiba. If this is off its gonna look like garbage!
2. Checked the mode for the TV. Is it in Zoom or Wide or some other distortion?
3.Checked the guns and lenses are they clean and dust free?
4. Check the signal @ the house. Every time you amp the signal, your amp adds noise as well. If your CATV signal is too low it still may not be above the noise floor. If you had a Spectrum Analyser(expensive) you could see exactly whats going on with the signal and wether or not thats the problem.

Good luck!