Think 4 23" will do fine.

I have 2 27" and it gives me a sore neck and shoulder because of the angles. The 2 23" in my office are much better ergonomically for me.

House using Loctek. Office has ergohuman.

Loctek one just screw on to the table. Seems stable enough for one monitor each stand (I bought single arm stand and added another one later). Haven't tried the multiple arms per stand, so can't comment.

The ergohuman one requires a huge hole to be drilled into the desk. Has two arms for two monitors. Think can add on more arms if you want 4 monitors.