If you are going to spend more than $50 on a pipe, buy one that you like, because it's mostly a matter of style with briars (and certainly cobs). You did good starting with cobs, which don't foul easily, and Grabow is a great bargain in briar, and as fine a smoker as any briar you can get. I own a couple of more expensive makes, including Peterson - they're beautiful, but they don't smoke any better than my Grabows.
Pipes made of meershaum (not to be confused with MM cobs - it's a carved mineral which is rare, and mined in few countries other than Turkey from what I've read) are actually worth spending upwards of $50 on, because the meershaum cheepies aren't carved from solid blocks. You would want one which is carved from a pure block of this stuff, not crushed and mixed with adulterants which are less heat-stable and will impart a bad taste to your tobacco. To taste only the tobacco which you are smoking, and never, ever the taste of smoldering wood, or the ghost of a previously-smoked fruity and goopy aeromatic from your built-up cake (you only build this up in wood pipes), which would mix unpleasantly with your fine English natural-leaf blend is one of the reasons why people buy these pipes. Other reasons include that absolutely no breakin period is required, the outside of the bowl stays cool in the hand, the material can be carved into beautiful figures, and good ones which are taken care of become more valuable as they age. But you don't ever want to drop anything made of this material. It is very porous, therefore dirty fingers will leave their evidence forever, plus it scratches very, very easily (so I learned when I attempted to scrub mine clean). Pipes made from this stuff are easy to smoke, but they really need to be handled with care.
I also have a couple of pearwood pipes from Mr. Brog, which I read is an extremely popular make in Europe, and gaining ground on the West side of the pond through Amazon. I love them both, although the stems aren't quite the most stout (I now have rubber bits on the ends of all my pipe stems for protection and comfort when clenching, so I don't care). After dumping the filters, they are fast becoming fine smokers for around $23. They do impart a faint taste (sweet, like pears) before you build up cake, but I don't find that unpleasant. Pear wood is apparently easier to work with, in that there are some incredibly beautiful figure-carved pipes available (they tend to resemble the meershaum carvings, plus aesthetics are made more complex from the hardwood grain), without the meershaum price). It's therefore softer wood, but my pear pipes, when smoked with my all-too-often hard puffing during the break-in have proven to be as heat-resistant as my briars. I caught a thread on a pipe maker's forum where olive, apple, maple, and a few other woods were recommended, but keep in mind that some woods are toxic, and the scary thing is that people are selling pipes made from toxic woods. I've seen a number of companies which are making them from toxic rosewood, and ill effects have been reported from smoking them!