The thread you saw is a good one. Those are good inexpensive products to get what you want done. The Lime puts out 10mW max. Every 10dB is x10, so an amplifier that puts out 20dBm is 100mW, 30dBm is 1W, etc. Gain is adding dB. So if you have a 10dBm output like the Lime and you have a 30db amplifier you get 40 dBm, or 10W. This is of course limited by the maximum power of the amplifier. Another useful relation is every 3dB is a doubling. 6dB is x4. You can feed one amplifier into another to keep stepping it up as long as you are not going over the input spec or driving higher than the output can go.