Take power from the solenoid? Do you mean starter solenoid? Surely then it would only come on when you are starting the vehicle? Or maybe I am wrong. What you want is a permanent live (fused) and an ignition live (i.e either tap into something that is only on when the ignition is on or connect to back of relevant part ignition switch. Or if you cant be bothered with having power to the stereo on ignition only, bridge the ignition and permanent live on the stereo.
Pics are useless really IMHO opinion of how to connect a stereo up as each stereo can vary to how the ISO connector is wired up...if you have the manual for it then it will say in there (although you can normally have a good guess if you havn't got the manual, i.e most ones I have come across are red perma power, yellow ignition, brown/black earth and the ones on the opposite block are speakers).
Lets see you speaker holder
Can you really hear a £4 wind up radio over the noise of a Series Land Rover?