A large chambered mouthpiece is good if you want depth and richness. If you want a bright high end, get a mouthpiece with a smallish tip opening, somewhere less than .100. Your exact choice will depend on the strength of the reeds you want to use. Meyer and Otto Link are two examples of large chambered mouthpieces, and you don't have to break the bank to get one in hard rubber. If you have the opportunity, try out a mouthpiece before you buy it.

I happen to know that Kirk is playing on a vandoren V16 8 HR. that might be a good place to start. I have one in my arsenal. 

Jody Jazz DV 7*.........:-)

Why not an Otto Link Tone Edge, maybe #5. They don't cost an arm and a leg and play just fine.

I would agree with trying some of the V16 pieces by Vandoren.  They are designed after Slant Links but also have a little bit of a contemporary twist to them. Jody Jazz, MACSAX and Ted Klum also have a number of excellent mouthpieces that are worth looking into.  The Jody Jazz HR and MACSAX D series are a great way to go if you are looking to keep the price under $200.00.

Although you wouldn't get a "warm" sound on the low end I would still try a Dukoff Silverite mouthpiece.  The "experts" I talked to said it was a "paint remover" but you may be surprised by the versatility. 

As an alternative to a new mpc you could get some modeling clay, the type that doesn't dry, and make a baffle with it. Start out with a piece of clay and roll it into a ball about twice the size of a pea and put it in your mpc to form a baffle. Try it in different places but make sure the outer edges don't climb up the sides of the mpc, and shape it like a wege. This will brighten up your mpc and give it more volume. You can also purchase plastic baffles that glue into the mpc with non-permanent glue. The mpc needs to be clean and dry for the clay to stick. If you like what the clay does then you can go to the plastic baffles which are a bit more convienient.