The next Ameritron solid state amp up the line from the ALS-600 is the ALS-1300. It runs 1200 watts with an IMD3 of -38 dBc.
Compare this to the AL-82 tube amp with an IMD of -34 dB, the AL-80 at -35 dBc, the AL-1200 at -34 dBc, or the AL-1500 at -36 dBc. None of these tubes amps can beat the IMD3 performance of the ALS-1300 solid state amp.
If you want a legal limit solid state amp there is the Prometheus DX1200L1.
It's interesting how the economy point for solid state at the 100W out level was reached in the mid-70's (solid state PA's replacing pairs of 6146B's in just a few years), and we seem to be straggling along at the 500W level (a healthy mix of 811A and solid state amps on the market... not that the solid state amps are new) but still not quite there at the 1500W level.
The big multi-multi contest stations probably don't benefit much from broadband PA's in terms of rapid bandswitching (already a dedicated tube amp for each band) but it would be interesting to see solid inroads as "spotting assisted" band hopping may become more common among HP ops in contests. A local ham friend has all this automated for band-hopping at the 500W level with a single solid state amp (not even a particularly new amp! Probably 8 or 9 years old at this point).