Unfortunately filters dont filter out the poor IMD products from these amps. Just because an illegal CB amp has filters does not mean that its automatically clean in all regards to its operation performance.
Clean in my book would mean using proper RF devices meant for linear RF service. Clean would also mean a well designed bias that keeps the amplifier clean IMD wise and stable. Most of these RM amplifiers are poorly designed regardless if they have filters installed in them or not, they garbage cheap CB products.
These days with the SDR receivers its very easy spotting hams who are using these garbage CB amps. They simple to out on the air because even the worst IMD performing legal ham radios even with all knobs cranked to the right
will not produce a filthy signal like that produced from a bad CB amp design.
If i bought any solid state amplifier I would want to be sure its clean in the harmonic and spurious products and departments. They should also be clean in their IMD performance. You wont find IMD specifications on any of these
amplifiers because the manufacturers probably dont know what they are. They assume anyone who is buying their products are dumb CB'ers
There so many good ham solid amps on the market why any ham would want to buy this CB garbage is beyond understanding.
RMITaly makes a series of HF amps with output filtering. I have one of the HLA-150 Plus amps bought used here. My spectrum analyzer shows the output to be very clean harmonics-wise. I found driving it past 90W starts to show distortion problems on the signal. This is consistent with Tom W8JI's report on this amp found on his web site. I am certain I could clean it up by tweaking the amplifier biasing but just have not had the time nor incentive to do so. It's a good QRP amp for the used price I paid and I use it with a K2 and Argonaut V.
I would NOT drive it to 150W. It can do it but the output will be severely distorted.