If you don't want to worry about second hand, there are some decent options, but you will need to spend a little more and the sub will have to come later.
Something like the TANGENT AMPSTER BT. It is small in size but has 50w RMS and a sub out, also includes bluetooth and optical in. It is £150 by itself though but well reviewed. You can pick up some Wharfedale Diamond 9.0's for £40 at the moment, both from RS but that comes in at £190.
You would also probably find with the above you have no need for a sub, for a desktop setup it will be pretty meaty.