I do still get mine done at the hairdresser because I want to be a natural red which is hard to achieve at home. Before I was so grey I used Excellence. It worked very well because it covered the grey but left it a little lighter so it looked more natural.
Could I suggest that you first try a lighter colour than you expect to need? If you come out too light its easy enough to go darker next time, but not so easy to lighten your hair if it is too dark as the colour tends to "stick" in parts of your hair.
I used to mix two colours; many of the brands have the colour tube and a bottle of liquid, so you can use half of one colour and half of another, saving the rest for next time.
Nice 'n' Easy didn't work for me as the colours were a bit too solid and harsh. My hair just looked too dyed. I really prefer something which leaves my hair more "streaky" and natural looking.
As others have said, do be sure to do the patch test just in case you react to the colour.