YES...
If you're using the Amiga for Video Toaster work and some AMIGA specific hardware like VLab, VideoToaster Flyer, DCTV, or Oaplvision, for stuff like animation and audio playback then every bit helps. Someting where the CPU is used intenvely. Lightwave comes to mind, but if you're doing Lightwave on an Amiga these days, you're either a massocist or have time to kill.
If you're doing any taks that can be achieved on a PC running UAE, you'll find that a $300 walmart PC running will outclass the most expensive Amiga CPU card. Do this all the time for programs like Adpro and Image FX, even deluve paint and personal paint. Want 4 megs chip ram? no probmem. Want an 060? just hit a switch.