The AMP you mention is for the sub so I assume you refer to the head unit driving the 4x door speakers once upgraded. The Kenwood seems capable of 22W into 4 ohm.
I have the stock business CD head unit driving the door speakers via PXE-650 then a separate Pioneer GM-D9500F AMP that is in theory 4x75watt but then I am not a)driving the amp at full gain (less than 50% gain) and b) not driving the (front only) door speakers to a point much louder than the stock system would have achieved in any case. All very subjective I know but I do wonder about the relative power of the sub compared to how hard you will have to drive the door speakers to "keep up"? You will however be driving all four door speakers it seems so you will be "one up" on my setup wrt volumes (I only have only fronts really powered up - rear set for background volume from the stock head unit only).
One point to note. Adding more power to the door speakers may not be the way to go - the Kenwood alone may be preferable. The SPS410 seem to like being hit hard above 400 to 500Hertz and not lower. Just adding more power to the doors will cause some distortions if you do not cut off the low end. If you simply cutoff the low end to the doors then you will have a midrange hole to fill (sub running with the doors). If you still have the under seat mids installed then they will take over but then you have to consider powering them as well and what crossovers to use for them and the relative sensitivities.
Suck it an see I think is the way to go ie the Kenwood driving the upgraded doors, the mono amp driving the sub.
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