Hi,
"Do I need a powerful, expensive computer for this!"
A loaded question
What I call powerful and expensive will be very different to your definition.
Have you thought about a low mileage couple of year of laptop of TradeMe ?? ( for overseas folks the NZ equivalent of EBay )
You can plug your current monitor into it and if your like me hate lappy keyboards you can plug your current usb kboard in and use that.
Then if you go away for a weekend etc unplug them and take the lappy with you, best of both worlds.
Most decent couple of yr old lappys will do all you ask above and handle normal image editing easily.
Also think about back up, if you only have one copy of everything ...... that hard drive will fail one day.
Your current hard drive can be put in a caddy and used with your new machine etc.
All the above is said assuming you are currently using a desktop computer.
Not knowing how far Nth you are, Harvey Normans and Dick Smith etc have some good deals at different time for end of line new desktop and laptops.
Short answer .... No .....
But shoveling pixels around in editing programs requires a bit of grunt.
As you update cams and your files get bigger you need more grunt and storage so buying bottom of the line is not an investment in the future either