I find I use my 4wt the most for trout in my local area. The only times want a bigger 5wt rod is when I'm fishing for really big fish (18" plus) and when I'm going to be fishing heavy weighted streamers. The 4wt is a really versitle rod and work well for both dry and nymph fishing up to about a size 6 hook.

I have a StCroix Avid (SCIV) travel rod and I like it, if you are trying to build on a budget you should look into the Cabela's Stowaway 5pc in a 4wt or 5wt. The blanks go on sale from time to time for under $40 buck! I perfer my Stowaway to the St Croix.