Speaker question

okay i have aftermarket speakers in my car, i was wondering if i can put a extra 2 in the back dash? I got 6/9s in there now and i want more sound , and i was wondering if theres anyway of doubling up the wires that connect to my speakers now to connect to 2 more besides them?

Your not going to get anymore sound out of it. The deck is designed for 4 speakers, if you loop those extra two, it will take more power, causing the deck to heat up, possibly burn up, the best solution would be to run an external amp and re-wire all interior speakers to that amp, and you can then add more speakers to the amount the amp will support... alot of work, not worth it unless your really serious about your sound, lol