I have heard that "overlining" a rod can help beginner casters get used to the feel of a rod loading. Since your rod is rated to take a 5 and a 6wt line, I would suggest using a 6wt line rather than a 5wt line and this may help you feel when the line is straightening on the back cast which can only help with your casting.

As Warrenp said, I also think there is a big difference between a cheap line and a more expensive one. In many books I have read, the writer has said that one should buy the most expensive line that they can afford. Many people may disagree with that, but i think as a general rule it is correct.

I would also like to echo the common underlying denominator of warrenp's response - Most of the line weights/actions/rod lengths are a personal preference and you should really head to a dealer that will allow you to cast the different combinations that you are interested in so that you can see what feels best to you. We could all sit here and dictate to you our favourite rods/lines etc but they should only be suggestions of the better ones to test. The final decision must be your own.

p.s - Notice how I avoided talking about the reel. I consider them just to be line holders when fishing small stillwaters, although they do come into use from time to time when the boss of the pond decides he wants to play with me, but that's not the norm.