Is High End Cable Really Worth It and What Brand

I agree with AVGUYGEORGE. You have a lot new already going on. Get yourself up and running. I would offer a point of reference. The discovery 123 speaker cable is a very neutral entry level cable. You might visit fatwyre.com, find your existing cable in their cable lineup and compare it to something like the discovery.

Cable is subject to tremendous markup. I would not buy cable from a dealer who is selling it at retail; it is too easy to buy great cable at discount prices.

I suggest you read the following site written by Roger Russell of McIntosh on speaker wire. McIntosh did extensive testing on speaker wire some time back and answered quite a few questions. Here is the link:
http://www.sundial.net/~rogerr/wire.htm
It is very comprehensive so be prepared to spend some time.

I use old Esoteric 8 ga wire; a friend gave me a spool of it in the mid 90's so the price was right!

High-end wires do measure better and they sound better particularly for longer lengths. If you want to see some measurements and analysis, see the Audio FAQ page at this website:
http://www.empiricalaudio.com

Do expensive cables make a system sound better ? Like a system  that cost about 10k sound a great deal better with 10k cables ?

As has been stated many, many times on this forum, it's more about system synergy than anything else  - certainly more than price. 

I've been in this hobby for over 40 years and have tried lots of different cables. While I certainly believe that cables make a difference to the sound, I've generally found I get the most bang for the buck using a cable made in fairly high volume using machines (not hand-made) with high quality materials.

While hand-made cables can be good, there is a lot of inconsistency in production, and the labor adds a lot to the cost. When I say hand-made vs machine, I'm referring to the actual cable itself, not the termination. 

In the last 20 years, I've made many of my own cables by using high-quality bulk cable and terminating myself. This allows me to get the exact length I need and use higher quality connectors than are often used by cable vendors selling complete cables. And save a fair amount in the process. 

There are a number of companies that sell good to excellent cable in bulk form including Neotech, DH Labs, Cardas, Canare, Kimber, Mogami, and others.

It's relatively inexpensive to experiment and find the best cable synergy for your system. In many cases, the connectors can be reused for another cable if you're not happy.