Lol, no I understand EXACTLY where you are coming from. Ive been an installer for 15 years now, I dont do many extreme systems. 100% of every client Ive had that wanted that amp was in the exact same situation you are in right now. And all of the ones I couldnt talk out of getting it, wanted something else within days of getting it installed.
The amp is marketed specifically around your mentality, Alpine did a great job because its an easy add-on sale. Its designed to sell easily to make shops money, not be cutting edge in tiny amp design.
The fact is you will buy the amp and spend a lot of time wiring it into the car, and once its all said & done you will be disappointed with the performance right from the beginning. On top of that you will also be out $150+ bucks and a days worth of your time. You will not have great luck selling it, and you cannot return it because the wiring will be hacked up.
Our ears hear logarithmically, and decibels (the measure of sound intensity) is an exponential scale. It takes a 200% increase in power to reach a 3db increase in volume, which our ears would perceive as around a 25% bump in volume.
A 150% increase would be barely a 1.5db increase, which is the border line along the threshold of human ear sensitivity. Does that not seem like a gamble to you? A lot of money & effort for an improvement you may not be able to hear.
The RF PBR300.4 is 75w x4, a 250% increase in power if using the same scale as the Alpine's claim. (basic algebra)
That means it should get you just over a 3db boost in output, or approx 25% more volume. Does that sound extreme to you? Sure doesnt to me, sounds a lot more like what you are after to me. lol
Now, this amp is available online for around $150. You do not need anything more than a 10ga power wire for this amp, and wire this small is very cheap. The price difference between this setup and the Alpine will be very little. The install is the only difference, and even that will not be much harder. We can also help walk you through it too, remember that. ;-)
And if that doesnt sell you off this amp, consider our hearing sensitivity. It is not equal, our ears are more sensitive to higher freq than lower freq. That means to get a noticeable improvement in mid bass (guitars, kick drum, male vocals) you need to increase them by more than a few db in relation to the upper freq spectrum. Look at an EQ adjustment, typically they boost by a db each click. You bump the mids up 3db and you have just increased the amount of power you need. There is a reason why speakers distort if the bass and mids are too high, and why you can crank the volume with the bass next to zero. A bigger amp doesnt just make the overall sound louder, in reality it can bring up all of the lower tones the speakers previously struggled with and balance out the volume across the entire spectrum. (often with the same peak volume level, but significantly fuller sound)