I have a feeling playing this game will probably turn out to be a poor decision on my part, we'll see.
If I were a typical stereo shop employee working on commission I would determine the customers budget, talk him into spending 15-25% more than his budget for items he "absolutely needs"
, and then sell him anything and everything I could in order to maximize commission/sales figures. Gotta pay the bills somehow.
If we are operating on the basis that "honesty is the best policy", I wouldn't sell any of them more power (well, except the last guy as he apparently doesn't have an amp, so any power would be "more power". Though I'd only sell him what's necessary to reach his output goals with the selected subwoofer in the selected enclosure for his needs, unless we are going for the "headroom" route). I'll focus on #2 because I'm assuming that's the bated "more power" question. I'll also assume that "regular street competitor" means he's a parking lot hero showing off for his friends and not competing in an organization since no specific class or competition organization was mentioned.
The reason I wouldn't sell him more power is because I fail to see the cost and time effectiveness compared to the return on investment audibly. By the time you factor in power compression you would need to more
than double his power output, plus the associated upgrades to the electrical system and wiring to even approach something considered "audible". What's the cost on that? Potentially several grand, before labor cost if it's necessary? Just to have an audible
change. Equivalent yields could easily be gained by evaluating his enclosure design relating to his goals/constraints/listening habits/etc, evaluating the subwoofer selection for his enclosure space & other constraints, acceptable alterations to the vehicle, system settings, current electrical system, etc etc. Adding power generally has the highest cost and the lowest return on increase in output, and that ratio only gets worse as you move up in power. You reach the the point of diminishing returns much more quickly in this area when we are focused on increases in audible output.
About the only time I really see "more power" as an acceptable answer is 1) SPL competitors seeking every .1db on a meter, by all means upgrade power until you can't gain anymore or you reach your class limitations, 2) the unusual & extreme circumstances where someone is running a mega-small amplifier on a mega-power subwoofer & looking to gain output. Increasing from 300w to 2000w on something like a BTL should obviously net positive audible gain....but really how many people with a BTL are presently running 300w on a permanent, full time basis and can't figure out why they aren't as loud as other BTL owners?
Once you get up into the multiple kilowatt range to start, I fail to see the advantage of increasing power for anything not chasing numbers on a meter when gains couldn't already be made more efficiently and effectively by other means. The required increase in power and added expense doesn't make sense for a daily driver, unless it's an unofficial penis measuring contest based on amplifier power.
Tell me what you would do in each case and I will tell you if your correct or not.
There's more than one way to skin a cat. There's not so much a "right" and "wrong".....responses will fall on a scale between more effective/lowest cost to lower effectiveness/highest cost. You'll have a hard time convincing me "more power", in all but extreme cases, is not going to fall on the latter end of that scale. Just because cone area can not be increased in a specific scenario doesn't mean there aren't other avenues to pursue outside of "add more power" that will yield not only more effective results, but also do so at a lower cost.