If you bought aftermarket splits and an amp you would get something pretty decent for $1300 installed. Close to gaurantee it would be better than this kit.
They say it's a Class D amp, 4 channel. The only amp Alpine makes in a full range Class D is the PDX which are quite expensive. So the amp isn't a fully fledged PDX, but you would think it's alright. Think it says 4x80wrms? That's plenty enough power. The let down would probably be the speakers, but I would love to hear it!
Alpine actually make quite a lot of factory systems for different car manufacturers so it would most likely be something that is from another car and not an aftermarket Alpine product.