6x9 speakers behind truck bench seat

I'm installing a simple stereo in my 78 F-250 Regular Cab truck, and I'm only going to be putting 2 speakers in it. I can't decide if I should put (2) 6.5" speakers in the doors (with sound deadening in doors) or (2) 6x9 speakers behind the bench seat. I think I'd get more sound out of the 6x9s, but I'm worried that the bench seat will muffle most of it. Anyone have any opinions? Thanks.

Put 6.5" speakers in the doors, the old hill billy trick of putting speakers behind the seats sounds absolutely horrible!2003 Chevy Avalanche,Eclipse CD7000,Morel Elate 5,Adire Extremis,Alpine PDX-4.150, 15" TC-3000, 2 Alpine PDX-1.1000, 470Amp HO Alt.