I have Mirage M5si's, and I'd be surprised if it benefitted from a different tweeter. Not saying it wouldn't, just that I'd be surprised. Seems to me the first thing to mod would be to upgrade the internal wiring so something like Kimber 4TC or 8TC, or if you could afford it, something in silver. The Mirage bipolar series are plenty warm and full sounding stock, so I think internal wiring that added some speed and extension would be a good thing. I think Cardas might add unneeded warmth.
The next thing would be what you mentioned, and I know nothing about it--would be upgrading the components in the crossover.
Next (or maybe first) would be to toss the factory-supplied spikes for some solid brass Mapleshade Heavyfeet or Megafeet, getting the contour that fits your installation, such as the carpet-piercing version.
I got improvements in speed and clarity by bi-amping or bi-wiring with one or two high powered, high current solid state power amps. I also got a lift in transparency and musical communication with the original version of the PS Audio Xtreme Bi-wire speaker cables. They listed at $1500/pair but I got them from Audio Advisor on closeout in 2005 for $349/8' pair. You might be able to find a pair for that or less now. They're incredibly stiff and can be a pain to attach to the amp, but boy do they open up the sound of that speaker.
I suspect that Kimber 8TC in biwire mode would work very well too.
The next thing would be what you mentioned, and I know nothing about it--would be upgrading the components in the crossover.
Next (or maybe first) would be to toss the factory-supplied spikes for some solid brass Mapleshade Heavyfeet or Megafeet, getting the contour that fits your installation, such as the carpet-piercing version.
I got improvements in speed and clarity by bi-amping or bi-wiring with one or two high powered, high current solid state power amps. I also got a lift in transparency and musical communication with the original version of the PS Audio Xtreme Bi-wire speaker cables. They listed at $1500/pair but I got them from Audio Advisor on closeout in 2005 for $349/8' pair. You might be able to find a pair for that or less now. They're incredibly stiff and can be a pain to attach to the amp, but boy do they open up the sound of that speaker.
I suspect that Kimber 8TC in biwire mode would work very well too.