HP Pavilion dv5-1177er upgrade. What cpu will fit?

Question

Computers

HP Pavilion dv5-1177er
Current cpu: Intel Core2 Duo T7500 (2 cores 2.2 GHz, TDP 35 W)
Motherboard: Quanta 3603

Compatibility is declared on the manufacturer's website (I didn't check it myself, it's written somewhere on the forums):
Intel Core2 Duo T9600 (2 cores 2.8 GHz, TDP 35 W)
On YouTube, one craftsman installed an HP Pavilion dv5-1070er (and offered on one forum):
Intel Core 2 Extreme X9100 (2 cores 3.0 GHz, TDP 45 W)
In the course of digging, I found such percent:
Intel Core2 Duo T9900 (2 cores 3.0 GHz, TDP 35 W)

Question 1: T9900 is not suitable? If yes, why?
Question 2: Are there more efficient processors for this computer? Again, if so, which ones?