I'd second this. I once was told to stick to the even weights (4, 6, 8) or the odd weights (5, 7, 9) when first building your rod arsenal. Believe me you will fill in the blanks later if you're like most of usI do most of my stream fishing with a 4wt or 3wt.
If you have a 6wt, I'd say get a 4wt. My favorite rod is an 8' 6" 4wt. The Redington Classic Trout rods have a great feel and aren't very expensive.
The Redington CT is tough to beat. My only other recommendation for a trout rod is the Echo Lift, a bit more affordable and every time I use mine I'm shocked at what a nice feel in hand it has for the price.