The custom built amps will generally do more wattage without frying with the same transistors. A 2 driving 4 Texas Star 667 will do 800 to 1000 watts and this is after upgrading the power wire and driving it hard. If you do this long something will likely pop. A Dave made 6 pill will do 800 to 1200 watts all day and last for years
The old 667V had a 2290 driving 4 2879`s, the new ones are two MOSFET`s driving 4 2879`s,
Driving either to the 800/1000 watt level will result in lots of ten ohm smoke in short order.
The heatsink is too small, and the driver is not necessary.
This amp was first built long ago when radios struggled to make a 4 watt key, today's radios being used on the CB band are capable of exceeding this.
The common dual final radio is easily capable of driving 4 2879`s to full ( sane ) output, the extra driver just eats up more current, and produces more heat.
Texas Star
Never designed to work on more than 14 to 14.5 V DC
Any more than that and all bets are off.
Never designed to take more than 1.5 or 2 watts dead key and not more than 20 watts PEP input power.
I also have a DX 500 that I use on 10/12 meters, have done so for years, it is a great amp and sounds fine as long as I keep output around 350/400 watt level.
The fuse holders are shit and need to be by-passed and you have to put a fan on them.
Mine was $300 and for me at the time, and it was a fair value.
If you search a bit there are gates here on the forum of me and Robb talking over 150 air miles mobile to base on both 10 and 12 meters on SSB and the radio and amp sound fine.
In the CB world, model numbers do NOT mean output levels.
X-Force
Will run up to 18/20 volts ( with original toshiba 2879`s) and at drive levels that will melt a Texas Star.
My 400-12 Base Amp ( "B" Bias) would put a 1K slug in the corner with a whistle in peak mode, but I would never run that amp at that level on 10/12 because at that point the IMD is outrageous.
Class C mobile amps built for CB keydowns were made for raw RF horsepower, kinda like motors built for Pro Stock......
2 cents.
73
Jeff