You need to use a sound pressure level (spl) meter or application to determine how loud you listen (use "slow" and "C" settings). Spl's are measured in dB's (1 dB is the smallest incremental difference in sound levels that the average person can discern). Most audiophiles do serious listening at about 80 dB, background noise is typically 40 dB, classical/jazz peaks around 105 dB, rock concerts typically run 110 dB, and the threshold of pain is 130 dB (all generally accepted numbers). Long term exposure to a constant 85 dB will result in permanent hearing loss and/or pain. Classical music averages 30 dB peaks, jazz 20 dB, and rock 10 dB. Dynamic range is the difference between peak and background noise.
Next you need to soul search to decide how loud you want to listen (maximum, ever) and if you'll be changing to less efficient speakers before you change amps again. As an audiophile I assume you want realistic playback of tone, detail, imaging, dynamics, etc. so do you also want realistic spl's?
Note that sound pressure level is logarithmic in scale compared to watts. So the sensitivity you indicated (90 dB/w/m) is based on 1 watt of input. Examples of dB vs. watts of gain:
1 watt = 0 dB of gain
2 watts = 3 dB of gain (a "half again" perceived loudness)
4 watts = 6 dB of gain
10 watts = 10 dB of gain (perceived as twice as loud, thus the logarithmic scale)
40 watts = 16 dB of gain
100 watts = 20 dB of gain
200 watts = 23 dB of gain
1000 watts = 30 dB of gain
So for your amp provides 14 dB of gain in class A operation which would be roughly 98 dB (depending on where you sit in the room) and 23 dB of gain in total which would be roughly 107 dB according to maty's calculator (thanks for the link!). So yes, you probably do most of your listening in class A operation. BTW class A runs full on all the time, so the heat generated won't change with the wattage being provided.
That's all theory, but in the real world the way manufacturer's quote their audio product specifications, especially speaker efficiency and wattage, varies widely. And as the above numbers suggest, that can easily result in needing 4 times the wattage. Another real world consideration involves the design of the amp (beefy power supplys and tube versus solid state work best). And of course you want to avoid sending a distorted signal (due to pushing the amp too hard) to your speakers because that's the easiest way to blow drivers. And my experience also indicates that for the best resolution (in terms of detail and imaging) the amp should have a commanding grip on the speakers (plenty of reserve power).
If your speakers were 83 dB/w/m efficient (not terribly uncommon) it would take about 2300 watts per channel to reach rock concert levels in your room! OTOH if your speakers were 95 dB/w/m efficient (again not terribly uncommon) it would still take 145 watts per channel to reach those same levels. So the best advice is to select speaker first, then look for a properly sized amp. If your speakers can handle say 100 watts or so, I'd say you already have an ideally sized amp.
