Verified answer

That will certainly work, but you're correct in assuming it's not going to be the best sounding system, and you might want to revisit the method you are taking to build the system, namely, the order. With the shaker 500 system, it is definitely advisable to do the entire installation all at once, because you end up spending less money in the long run, (between installation costs, and the parts required to bandaid together the components until you're done)

I would recommend starting with the amps first, since the biggest issue you are going to face once you start replacing speakers is that the shaker amps are a piece of junk that really doesn't have enough power to push a modern day cone, so your first step would be to install a powerful 4ch amp (you'll have money if you have the mono for the sub installed at the same time) I would then follow this up with the deck as soon as possible. Followed then by the sub, and eventually the door speakers.

As for the choice of equipment, stick pretty closely to a brand (at least between speakers and 4ch amp). Kenwood is a good brand, JVC Arsenal's a good brand, Dual and the shelby speakers are both crap though. If you want a pretty good system for the money, take a look at doing a simple JL, Alpine, or Kicker system.

JL C3-570s in the Front, JL C2-570s in the Rear,JL 8W0-4s in the door panels, and a single JL 12W6v2 in the rear would sound pretty sweet, and you could pair this up with pretty much any head unit you preferred. (I personally like the new Kenwood Digital Media decks) And for the amps you would roll with JL XD600/6 running the speakers and 8's, JL XD600/1 amp running the sub.

Hope this helps.

if u have 1 shaker 10, u have a 500 watt. if u have 2 10 inch shakers, u have a 1000 watt.