New Roc is on order, build date confirmed for next week


So I need some advice on what my options are. The car is leased so I really don't want to go about changing speakers/headunits etc, but I'd love the standard setup to have a bit more power. On previous cars that I've owned, I've been happy putting in an aftermarket stereo with standard speakers. I've currently put a Sony MEX-BT5000 in an ST170, which only takes it to 4x50w, but the difference is sound quality from the standard headunit is amazing and the speakers cope extremely well even at high volume.
I've seen this amp mentioned on here (http://www.bluespot.co.uk/car-audio.asp ... -amplifier" onclick="window.open(this.href);return false;), and it sounds from the writeup that it will happily integrate into the standard setup, but will 4x150w just be too much for the standard speakers?