Buy better amps for starters !!!!
Some people might not agree with me here but I would recommend buying a Genisis 5ch Amp and run the whole system through it. A lot of people swear by running dedicated amps for subs however I have heard a lot of systems and would say that unless you are thinking of spending serious money on speakers and getting them set up / Installed properly then the 5ch is all the amp you will need.
You should be able to pick up a second hand one for perhaps £250 - £300......