The 6900 chassis is known to drift a bit until it is warmed up. The 6300 is just a 6900 board sans the SSB components. Both are the basis for some loud modulating AM radios. There may be a few 4 pill Ranger and RCI radios around that were converted using an amp board with genuine Toshiba 2290s or 2879s. I believe the C4 version they were called. R&R also offered them as an add-on a few years back.
I would also look for the older 6900F150, Turbo or Jumbo that had genuine Toshiba transistors in the final amp stage. These older 2 pill versions of the 69ffb4 radios hold their value though. You may get a few more watts from the new ffb4 version but I don't trust those DEI or HG final amp bi-polar transistors as far as I can throw them.
Some of the new big radios like the 98VHP and 2970N2 use 8 MOSFETs and I know how that story will end. Luckily the MOSFETs are not that expensive. Make sure the bias is adjusted on these MOSFETs to match your 14.5VDC+ or higher voltage power supply (if used)
The main issue with all of them is that are not adequately fan cooled or not fan cooled at all. Probably due to the fact that these were marketed to OTR truckers that were light on the key down times. If you want to run then as a base station, simply put a cooling fan nearby to blow on the bottom of the radio to get some more air movement on the heat sinks.
Either way the 69ffb4 is a limited production radio that will also hold it's value IMO. Not really trying to bash it, I just like the previous versions better. Look at the prices that they are getting for the big old RCI base stations these days. Literally more than a new HF HAM radio.
New "Black" Transistor crap?
Hmm, well looky here... R&R offering the amp board with Genuine Toshibas still. You Solder. $450... ouch.