I'll start with this, so we can get it out of the way early: Nobody can tell you what you like. We can make suggestions, but you have to try the mouthpieces yourself and make your own decision.
Now that's out of the way...
If you're just looking to get a little bit brighter, you might want to try an Otto Link Super Tone Master (metal) in a tip opening somewhere around a 5-7. That wouldn't be a huge change in feel or resistance, but the STMs, in my experience, generally have a little more material in the rollover baffle. Another option in the "somewhat brighter" range would be the Vandoren V16 hard rubber mouthpieces, or so I hear. I can't tell you too much about them, since I haven't tried them, but based on what most people who have tried them have said, they're a little brighter than an STM. How's that for a convoluted sentence?
I would characterize the Link STM as a mouthpiece that's on the bright side of dark. For a more middle of the road mouthpiece, you could try a Berg Larsen /2 chamber or a similar mouthpiece (medium baffle, medium chamber).
If you want to get BRIGHT, you can go for a Dukoff, Vandoren Jumbo Java, Berg /1 or /0 chamber, Rico Metalite or other high baffle/small chamber combo.
These are just a few options that you might want to look into as a starting point for finding the right mouthpiece for you. They're all under $200 (I think) and a good example of any of them is a great mouthpiece for somebody, but not necessarily you. Of course, there are many, many more mouthpieces out there, and I'm no mouthpiece expert myself. I just play the things!
