The glue is normal. It holds the heavy transformer in place so rattling doesn't break the solder joint over time. Those transformers have quite a bit of copper wire on them, thus a good bit of weight, imagine if they were just solder and the amp was mounted on a vertical surface... now say you hit a huge bump in your car... use your imagination //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
Heat is a also non-issue for these amps at any normal load. The transformers operate well within tolerance even after extended periods of time.
Hope that fully answers your question!