wow 150 W rms (per channel) amp recommended for a 40 W RMS speaker? Sounds about 4 times too high if you ask me.
For best results, try to match RMS levels. If each speaker is rated for 40 watts RMS, then look for something around 40 watt RMS X 4 Amp. (It'll be much cheaper, and you won't have to sacrifice quality or brand name to get the power you want) With an alpine Type -S you may be able to do roughly twice the power without much worries. I was putting 75 watts RMS to a 60 watt Polk 6x8 and never looked back. I also have used the same speakers for almost 3 years, and still felt it worth while to keep even after selling my truck.
Doubling the power may give you 3 dB, but at an eventual cost of longevity. Just depends on what trade off you want to make.
p.s. A perfect match for your speakers: