I decided to change the stock front speakers to a pair of 6,5 inch aftermarket ones. It was quite easy. Both adapter rings and Cable adaptors are available from Connects2 in UK. It doesn´t say on the website that the adapter ring fits the Mirage but it does. I bought the stuff from :http://www.nexxia.co.uk/ and : http://www.dynamicsounds.co.uk/
The adapter ring is CT25MT02 and Cable adaptor is CT55-MT01. The only thing i did was to drill 3 new 4mm holes to fix the adapter ring in Place. I used 4x35 mm screws and locknuts. The speakers i put in are from DLS which is a Swedish brand. The sound got much better.
How to remove the door trim you can find in older posts.