It is always best to use three spikes. They should be driven clean through any carpet and padding into the plywood. Three spikes on tile is OK as long as you lower the speaker gently.
The best digital signal processing units sound like whatever you make them sound like. You can create any target curve you like within certain limits. After 25 years of doing this I can look at a curve and tell in a general way what the system will sound like. You can not determine imaging this way. I have to see measurements on each channel separately to get an idea, again in a general way. The best units are now using 64 bit floating point systems with powerful processors. They run at a minimum of 24/192. There is no characteristic sound. It all depends how you program it. Most system like Dirac Live run on their own algorithms leaving you little room to play. You have to accept whatever they do with minor adjustments. With my old Tact and the new DEQX units you can let them do their thing and walk away or you can grab the bull by the horns and program the unit yourself which IMHO produces the best results once you learn what you are doing.