iMac G5 questions.

Hi guys this is my first post, im soon converting from the dark ages, and buying a beautiful Mac. I have finally decided to buy decent hardware to make my life easier.anyways straight to the questions.

1.I have noticed that all iMac's come with a standard 256mb of ram, is that enough for me? basically what i want to do with the computer is make some pretty basic video's and music. midi keyboards and synth's.

2.Should i wait for os X tiger ? and then just purchase my computer then ?

3. is it easy to use external hard drives on a mac?

thanks guys. oh and by the way
im on a computer at work right now that uses windows me...BOO!