keep your reel. go get a quality fly line. i'd recommend the scientific anglers mastery series wf5f gpx for you. replace your bass pro line with this one. yes, i said a 5-weight line on your new 4wt tfo ticrx. that is a pretty fast action rod (stiff) and you will want to over-line it by 1 wt when fishing for trout and pan fish. you will find it much more pleasant to cast and fish in a wider range of situations. so much for equipment.

15 yds is respectable for a standard, single-haul, pick up-lay down cast with a couple of years of fishing under your wader belt. when we talk casting distances, we talk in feet. that's 45 feet. unless you're fishing streamers, you shouldn't need more than 45 feet for anything you would use a 4 or 5wt fly rod for. but...since you seem to want more...neither more practice nor more expensive/different gear will increase your casting distance to any signfiicant degree. changing gear to the best possible combo of line and rod might tack on 5-10 feet...max...maybe. so what will help you increase distance?

1. tightening your loops and adding line speed to your casts. a nice tight loop w/the fly and rod legs no more than 2' apart is transferring energy more efficienty from body to rod to line to fly, is far more aerodynamic, and (thus) carries further than a wider or asymmetrically formed loop. adding line speed to this nice tight loop form increases the energy to target. you do this by reducing slack in the fly line and adding just the right amount of smooth acceleration to your casting stroke. when you make these improvements to your fundamentals, then more practice will yield more distance. in other words, practice doesn't make perfect. proper practice makes perfect.

2. once you get #1 down pat and have hit yet another plateau...probably somewhere between 55-65 ft...if you want to add any more distance, you will need to learn to double-haul to increase line-speed even more and to "carry" more line in the air during false-casting (used to generate the requisite line speed and length prior to the presentation cast). with the double-haul, you can effectively lengthen and slow your casting stroke beyond what would be possible without the extra haul. this is what allows you to carry (or aerialize) more line without crashing your loop.

finally, i'll give you one free piece of advice about adding distance to any fly cast: be very careful/vigilant not to allow the desire for more distance to surpass your desire for better form. the more distance you want to cast effectively, the better your form must be. there is no way around this. and the perfect fly cast is nearly effortless.