I've had the alpine, the infinity, and the dayton.
For comparison
Infinity has great SQ and good sensitivity it can get loud off low watts and sound good doing it, but it cannot handle high power.
Alpine Type S has good SQ will get moderately loud, a type R will ger very loud and hits the low lows well, but sq will be lacking a bit
Dayton HO has the best SQ and will get loud, but it requires more power.
In my opinion all very nice budget subs.
As for the question about the amp and enclosure on sonic, that enclosure will actually work very well for the HO 12, that volume is very close to the necessary size needed to have as flat response as possible from that sub, that being said you may want to mount the motor side of the sub on the outside of the enclosure for the best sound. I don't like prefab boxes, but if they are done right, they are just fine for a sealed setup. I would look into a nicer amplifier though, I just don't think that one is efficient enough for you, don't have any experience with it, but I'd go with something else. Maybe check out the MB Quart Onyx 1000D It will have a little overhead as far as power goes.