Something quick and simple would be to spend about 250 on a pair of wharfedales and look for a vintage receiver or maybe a stereo HK receiver. I personally would look around the classified sections around you to see what people are selling.
For my first setup, I went to go get a cheap onkyo receiver for ~160 and a pair of paradigm titans and a paradigm center for ~150. You could always keep your sub you have now but I would recommend to upgrade it if you ever get the chance. Obviously you might not get the same deals as me since the titans and a center for 150 is a really good deal. However, if you budget around ~150 for a vintage receiver (got my pioneer sx 838 for 175 which i powers much better than the onkyo) and then use the rest for speakers, I'd be very surprised if it doesn't improve what you have now.
All my numbers are in USD so that should mean you might be able to get more for your money than i did.
I wanted surround sound (for films etc) and to listen to music too. Ontop of this I did not want multiple amps and multiple speakers. Yes an AV amp compromises audio/music listening, but I'm willing to suffer that for a simple/less complicated/less cluttered life (My 15yr old bi-amp Sony stereo which now lives in my study blows my AV system out of the water when it comes to music)