ok here goes im just starting to put together some ice and now im looking for advice on amps and speakers is there a ratio involved or do i just match the wattage of speakers and the amp help me im clueless

I might be in a position to buy some mint 18" escort wheels.   I need to know this, If i fit them will i have any issues? Basically the car is not lowered and i am not interested in lowering it, the tyres on the wheels are 215x35x18, i have read that this is fine and i should get no arch issues either   Is this all good or am i asking for trouble?

Can anyone give me the specs required for a good sounding bass box for 12" subs. Preferably dimensions, diagrams, suppliers, anything so that I can get some decent sound from the boot on my Mk V cabbie? Please help!!