I have been very close to ordering the t.bone CD 56 Beta for exactly that reason since i compared alot of soundclips on Thomanns site in search of a good tom mic. We already have a cheap TSM set (from 4sound) that has worked ok so far in combination with the other mics we use on the drumkit, but it would certainly be interesting to try out this mic and i am still very tempted to order one to test out.
If you compare the soundclip of the MD421 and the CD 56 they actually sound very similar on most sources they recorded and the MD421 cost very close to ten times more than the CD56.
Compare for yourself. the t.bone CD 56 beta - Thomann Cyberstore Sverige Sennheiser MD421U-2 - Thomann Cyberstore Sverige
I have also found that the t.bone MB85 beta mic ( i have bought three myself) is a better alternative to the SM58 at well below half the price (almost a third), it actually sounds very close to the shure beta 58.