Here's an interesting Peavey patent. 

http://www.freepatentsonline.com/5524055.html

"... Thus, the output tubes 16 and 18 become over biased beyond class-B and at severe output clipping significant crossover distortion is generated as well. Consequently, at overload, the output signal of tube amplifier 10 will be clipped at the peaks. However, it will not be as "dirty" as a typical solid state power amplifier operating under the same conditions, because a large portion of the overloaded output waveform is forced or compressed into the severe crossover distortion region. To a musician, such a waveform is much more musical in nature and "cleaner" (i.e., less harsh) than a solid state amplifier at overload. Due to the compression (i.e., distortion near the zero crossover), the actual peak output clipping is reduced and is far more tolerable than that of the solid state amplifier. This phenomenon is thus, tube power amplifier compression."

There's circuit schematics that simulate this type of compression.

I commonly see diodes for clipping, but never anything for adding crossover distortion, and the effects it has on clipping.

I ran across these:
http://www.oliveaudio.com/index.php?page=1

Click on the "ULCA"  link.

They are from Lars Clausen who started www.LCaudio.dk but is no longer with them.

The ULCA3 - Single ended Class-A looks like a lot of fun and ultra-simple and potentially a great sounding amp.

Take a read at this: http://www.rane.com/pdf/old/note128.pdf

Limiting can be used to prevent clipping, but this doesn't get the maximum drive out of the amp. Lows usually cause the clipping.  During bass clipping the high frequency of the input signal has not clipped and thus is still allow to gain DB's.   The lows compress far before the highs ever do.

I'm thinking the key to squeezing out the maximum from a lower wattage SS amp is to allow the lows to clip, but when they do start to compress the highs.  In other words instead of limiting the whole signal just limit the highs.  The amp will still clip and add "some" high frequency content, but as much as people believe.

This just might be the key to squeezing out the most from a small SS amp.

I ran across this study
http://milbert.com/articles/TvsT/tvtiega.html

The amp in the study was a standard old BJT.

If you've ever been on the edge of thinking SS wasn't good enough you'll appreciate that 25 years later, SS has only got better. 

I would love to see a new study done.