I HIGHLY reccomend the smsung 181T and the 191T as far as size goes get the 17 you have a higher reslution than a 15 so you will be able to put more stuff on the screen
I went from 4 to 7, with 5 19" and 2 smaller ones for trading platforms. For what it's worth, success on trade analysis increased markedly with several monitors dedicated to things like compq, time and sales on my core stocks, more room for the technical things I watch. Found really low prices on ubid, other sites. Good luck