power supply....

Should be ok. Remember car stuff is designed to work best at 13.8 volts rather than 12. Using the lower voltage will reduce the maximum power from the amplifier. But power supplies designed for exactly this purpose are readily available.

Your biggest problem might be connecting the radio unit to an aerial.

No. This is a newsgroup.

Yes. Try for 13.8v, though.

No.

The radio will only drawl the amount of current it needs (about 1.5A) even if you use a 4A or larger capacity power supply. That might change if you crank the voltage much higher than the nominal 13.8V others have mentioned but then you stand to damage the radio. No matter what voltage you apply to the radio it won't make it sound better but better speaker/s might.

Rush

Although the nominal vehicle voltage is 13.8v, it is not at all unknown for the charging system to go well beyond the accepted maximum of 14.2v - sometimes as high as 15v. Any vehicle based radio should be able to withstand up to 16 or 17v, without complaint. CB power supplies are plentiful and cheap, and are specifically designed to power vehicle based radios, in a home environment.

Arfa

You can't hurt something by having more current available, the radio will only draw what it needs. Car batteries are capable of hundreds of amps for short periods.