After reading a lot of discussions in the forum i come up with the following:

I always want to see things in proportion. 2-way systems mostly mis something in the sound they produce.
I think that sub-bass can only be produced with woofer from 15" and larger. then is the logical step that 1 15" woofer, needs a 12" for mid (or 2 8") and 2 15"-es need 2 12"-es.
And double 18" needs double 15".

The Eminence lf are ment for subbass, so if you would cross them above 1k they won`t sound good.
Do almost all the PI speakers use 2-way with passive crossings?

I dont consider passive crossing networks handy for the purpose i use the loudspeakers. A active crossovernetwork is far more better than passive. I also use a compressor/limiter for the wellness of my set.
so if you people would really hear something nice, try a active system.