Will a high quality preamp really make a difference in sound?? Also speaker cable

Every system is a different, but a preamp makes a difference in my system, and so do the cables.

Using junk cabling is a sure way to prevent your system from being optimized, and evolving into something special. With the options available today, there’s no reason to risk the cables being the bottle neck of potentially good system. There are lots of good reasonably priced and DIY cables. Mogami, Blue Jeans, Carol, Belden, SKW, Monoprice, Audioquest, GearIt, and others. No need to spend a fortune, but good cables should be quite audible.

Yes and Yes.  

Yes to both

I think the preamp is the most important component in the chain.   I usually spend over budget when I replace a pre so as not to make a lateral move.  

Unless you've had a world class preamp swapped into an already good system. It's hard to explain how pronounced of a difference it CAN be.  May take trying a few but a great one can really elevate your system to a different level.