np and to answer your other question...some mono amps have 2 'channels'. it's still a single channel amp, it just splits internally into 2 terminals. they do this so that you do not have to cram the wiring into the same channel, and so that you can use the biggest wire possible.
and an ohm, yes is a measure of resistance. it's not a matter of 'wanting them or not wanting them' because all the things have to match up in the system. some amps cant get down to 1 ohm, while certain wiring on subs will give you a 1 ohm load. so you 'dont' want that 1 ohm in that situation, while in other situations you may have a 1 ohm stable amp, and want to give all that power to your sub. so it all just kinda goes hand in hand. keep reading around...you'll learn a LOT