What kind of meter are you using?
Your numbers are going to vari depending on the meter used.
A meter that reads AVG watts will not show you what the amp is doing peak.
The 400 uses 4 x 2290 that are approx 60/80 watt output transistors, so on AM you do not want to run much more than 80 to 100 watts dead key.
The 148 is a good radio, and the 3900 is a good rig as well if you want the extra bands, really as far as it goes you will be hard pressed to find something that has as good TX/RX than the radios you have without more $$$ as you put it.
Most exports will not offer much more than more power out of the radio, more bands than the 3900, and other things like lights/freq counter/echo and other add on`s and you will just have to turn most of them down to prevent over driving your amp.
Have a look at this Vid:
Texas Star 500V Performance Report - YouTube
I know it is a 500V, but pay attention to what he says about the meter, if you apply the same idea to the 400 using the built in meter, looking for output in the top 2/3 of the scale and forward power, you are set up fairly well even if you have no external meter.
73
Jeff