As satellite speakers in a sub/sat system, they're as good as any in that price range and when they were current, they were about £450, but that included the 309 sub and 304 centre. In this setup, they won several awards.
However, they wouldn't be much good without a sub, as they only go down to 100HZ frequency wise. You're looking at about £200 for a sub, unless you already have one; that's £350 in total. At that price you have other options for a full 5.1 kit in the discounted Q Acoustics 1010i or the similarly priced Wharfedale Diamond 9 HCP kit.
Also, what amp would you be using them with? the MS speakers are bright sounding and work best with warmer amps such as Yamaha or Denon.