Supakit, adding to the above, I suggest you AUDITION a reasonably priced tube (good recommendations above, IMO) on yr Mac. You like jazz, percussion, etc, if I read correctly, you will appreciate transient attack. So, go for a tube pre w/ good power supply, and fast. You may want to try a tube that matches *reasonably* with your Mac -- keep in mind that you may wish to chage yr amp in the near future, as diver suggests. In my (limited) experience, doug's suggested melos offer superb sound. Again, IMO go for reasonable sound w/ the Mac: you may be keeping yr new pre and looking for a new power soon enough.
Good luck!
Good luck!