The Celestion-Truvox-0820 looks like a direct upgrade to the HT-8 drivers (barring crossover changes that may be needed) and they're coming in at the same price (for now) as the old Celestion TF0818-8. 2-3db more sensitivity, 2db more power handling, 5mm xmax vs 3.25mm xmax. All pure upgrades, I checked the sensitivity based on the graph, not the number listed.
I just pulled the trigger on some HT-8's. Would there be any benefit to applying sound deadener to the inside panels? Something like this: I saw some pics of someone else doing it but was wondering if there would be any advantages to it in the HT-8. I've used it extensively in my cars and it helped tremendously to dampen vibrations and make my stock Bose system sound better.
No harm in applying that material to the cabinet walls of the HT-8, but the difference in panel resonance won't be nearly as noticeable compared to sheet metal in a vehicle.