how can choose transistor in a power amplifier!

Hi guys,
I want to design an power amplifier,With the following specifications:

Frequency range 1400 ... 1600 MHz
Input power 1W(typical) , 2W (Max.)
Output power P1dB min. 45 W (CW)
Saturation power Typ.60W
IM3 @ 45W PEP min. -30 dBc
efficiency 50% @ 45W
Gain (small signal) Typ. 17 dB
Supply voltage +28 V DC
Quiescent current typ. 550 mA
Current consumption 3.5A @45W, max. 5.5 A @ 60W

Applications of this PA is Digital broadcast systems (DAB, DVB) and COFDM systems using modulation types QPSK, QAM ...
now My question is that:
1. how to choose transistor for this power amplifier?
2. There are so many class types for RF PA.Which class type should I use?

Only linear PAs (class-A or class-AB) are suitable for QAM and similar modulation schemes involving amplitude information.

Major manufacturers have device overviews sorted by frequency and power range.

In these power ranges, GaN transistors are very popular nowadays.
Cree,Nitronex,Triquint. Macom...