The A500 doesn't have a hard drive controller built-in so that will be an add-on. The A1200 comes with a laptop-style IDE controller that can be adapted to either an SD card or, more easily, a CardFlash card. CF cards use an alternate pinout to the IDE protocol which is why I say it is easier.
As for the monitor, you'll probably want a scan-doubler to convert the horizontal sync rate to be 31 KHz instead of 15 KHz. There are cheap ones that are designed to be used with arcade cabinets but I've heard that European SCART adapters to HDMI are cheaper than Amiga-specific pinouts. Getting an adapter from Amiga to SCART might be easier too because Amigas are mostly European beasts due to Commodore's ineptitude in marketing here in the U.S.
Other, more expensive monitor options might be using component video inputs instead of HDMI. The adapter costs as much as the Amiga->SCART->HDMI combo but leverages the analog to digital conversion some TVs already have built-in.
