Ok currently i am using a 2 way setup with an audio control 6xs,
I have handy a set of dynaudio D54 dynaudio horn loaded midranges, I was wondering if its beneficial installing them in my car, the specs are 200watt rms nominal (1000watt peak transient 10ms) 8 ohm with efficiency at 93db 1w/1m (which is 3 db higher than my splits)

I know it would be an extreme over kill and i know i will never power them at 200watt rms @ 8 ohms (effectivly 400watt rms 4 ohm amplifier)
From a sq point of view i just wanted to know how i would do it and is it worth doing? (currently only have a 4 channel amplifier, another 2 channel amplifier or a 6ch amplifier total is required) i know i can set the audio control 6xs up to run a 3 way setup aswel.

Also i'm on the lookout for some new tweeters as the ones i was using are no longer functional, I would even consider swapping my midranges (if they are of no real use) for a nice set of splits or even high end dynaudio tweeters, morels or something the like. If you have anything give me a pm please

The mids will only help if you need them. I would rather use a 2-way system, but then would be 'missing' some midrange frequencies.

I run my Dyn mids (8ohm, 120W) from a 75W amp no probs.

the fact they are 3dB higher sensitivity means that at 1/2 power they will be the same loudness. what power is the rest of the system running?

my amps are all 75W/channel, but the actual power to the speakers is more like 50W midbass, 10W midrange and 15W tweeter.

for tweeters, get the best ones you can afford, which will work in the required frequency range for your system.

Your midrange is the most important speaker for imaging and staging. Also how it ties in with your tweeter is critical. Being a horn, mounting is going to be very difficult indeed for the best results.

Like Pulse, I'd stick with two ways or think about a different mid. The amount of power you need for most mids isnt much, slightly more then tweeters. More power simply means more headroom.