Bumped on an interesting article the other day: a cheap power amplifier with two MRF300AN LDmosfets from NXP.
The MRF300 produces about 300 watts @ 50V and operates broadband from 1.8 – 250 MHz. Razvan M0HZH created a little power amplifier with two of these mosfets which put out around 600 watt with 4.5 watt of drive power.
This is a really nice project which is going on my to-do list!