New Imac- What sound & speaker options?

Having made a recent transition from PC to Imac the only shortfall in my opinion is the sound ...as reported in other recent posts.

I used to have a Creative Inspire T7700 7.1speaker package that I hooked up to my PC which died recently hence the Imac. I would listen to downloaded music from itunes and  my own ripped CD's whilst on the PC and was happy with the sound it produced.

I initially started to look  for an interface to use the creative speakers with the Imac but have since dispensed with this idea 

Installing some active speakers such as the B & W  MM-1's is a further option I am considering but although achieving the full five star accolade some reviews are not that complimentary. I  have a budget of about £400. I dont need massive bass my genres are mainly electronica if that helps.

I am open to any suggestins to improve my listening exerience with the Imac