You realize that the 'aside from filtering' is the entire issue, a fairly expensive one to address and one that will take a lot of time with a station monitor and other bench equipment?
An amplifier circuit is trivial. An RF amp that is tuned for a band and meets spurious emissions and is linear...non-trivial.
There's a reason why the SGC and Ameritron mobile amps are priced as they are.
To be fair, a year ago, I came here asking similar questions and spent a lot of time reading and learning to finally understand what is involved. Don't run CB amps on HF, they are dirty and people will be interfered with by your splatter. There are plenty of people out there now with spectrum displays on their rigs and they are glad to send in reports on dirty signals.