How hot is too hot?

70 watts is 70 watts. 
Specs says it idles at 70 watts. That is going to be warm to the touch for me an old mechanic and HOT to someone that has girly man hands. :-)

Regards

My FW J2 runs hot. That is even taking the nerve damage to my hands into consideration. It sounds great,and makes a nice space heater in the winter months. I wouldn’t have it any other way. I also don’t leave it on 24/7.  It takes about an hour or so to hit full stride. 

Call Parasound and ask them.  They might say it's normal or they might want to have a look at it.  It might be running hot because of a problem like hf oscillation or a ps problem.  

Depending on the safety standard used for compliance of this unit the maximum temperature of operating device on the surfaces that a user can touch is 70 C (158 F) for metal and 95 C (203 F) for non-metal surfaces.  That's pretty hot, so a prudent manufacturer would allow some headroom as not to burn paying customer :)   It is easy to check with any infrared thermometer.  If the enclosure is not black, put on it a piece of thin black electric tape, let it sit for ~15 min. and test - non-black surfaces have emissivity coefficient which you may not know right off hand.  If the temperature exceeds the above numbers to me this would indicate either a) non-compliant design, or likely b) something went wrong and needs to be addressed, preferably right away.

I have an esoteric f03 and idle is 300 watts.  It is uncomfortable to the touch for more than a few seconds.  Have to turn it off when not listening here in Tampa   The best of tube and solid state sq.  75 watts is a lightbulb left on