Like any lite action rod the lower line weight will give you a more sensative bite..But I would say go ahead with your 4lb test..
I myself when fishing for larger trout use fireline. i know a lot of guys dont like it, but I do. You can go heavier using the braids...I have 2 rods one is done up with fireline 6lb (I think) and the other is 2 pound trilene micro ice.
good luck and enjoy