I would not recomend the 667 as a good platform to start with because of the built in driver. Gain is going to go up as you go down in frequency and it is already a beast as it is.
If you really want to do it right I would sell the 667 as they are a popular CB style amp and put that money towards a real HF amp.
In the long run I think you will come out better off.
73
Jeff