You would do a little gain matching with your pre-out level from the 4400 and the input of the 3802, but not hard to do (you'd need to do the same with any amp with gain controls).
Generally larger speakers tend to be more sensitive, so easier to drive in that respect. 100W is better than 60/70w.
I own one of the Crest 2208s. It is perfectly fine for hi-fi use (it's no less suited than Verdinuts QSC "PA" amps used in movie theaters
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),except for the quite loud fan noise, which won't be a issue for you; it also has phoenix connectors, so a little more work to use it with pre-outs from the 4400 (which are rca). I built cables to do that for mine. By repurpose the 3802 I meant not as power amp but use it in another system elsewhere in the house/garage....