I suppose that 6" rounds would fit, but you'd have to drill some holes and fill the voids left by the 6x8 opening. I was reading a post earlier today by someone who said that they made a plexiglass plate to mount some 6" round speakers to AND they mounted a tweeter on this plate then screwed the whole shebang to the stock opening. He said it worked well. Food for thought, huh?

'99 Sport TropicGreen,Duratec, SVT exhaust, Brembo rotors, Ceramic pads, K&N filters(oil & air), Alpine CDM7874, Polk DB570 speakers front and rear. Fog light mod. 50% Formula One tint.