Man, I wish I'd had anything more than a crappy little combo when I was fifteen.
One of the most important lessons I've learned in terms of being on the gear market is to always try everything you can to make the best of what you have. It can take a little while to get the results you're after out of the gear you've got, but it can happen.
Little anecdote. When I was around 21, I was playing in a crappy covers band doing all sorts of funk-rock numbers and what have you, and because of the style of music, the bass sound was important. In that year I must have dropped about two grand on gear trying to keep up with what I thought I needed, and still I couldn't make it happen. One evening we gigged with this other band, a bunch of fortysomethings playing blues and classic rock stuff, and the bass player had this incredible sound, lots of beefy attack but really mellow, harmonic tone. I talked to him afterwards, and he showed me what he was using: An old Fender P-Bass through a Trace Commando, with a little EQ pedal and a compressor. His whole rig must have cost about a quarter of what I'd put down on mine, and his sound blew mine right out of the water.
So I sold most of my gear and made myself start from the ground up with the basics. A good bass, and a good amp. That's pretty much what I use now, and if at any point I feel like my kit is underperforming, instead of repalcing it what I do is spend some time with it, trying to figure it out, trying it in different situations, reading up about how to make various settings work for me. And usually that works fine.