You can put a pair of 3-1/2" speakers in the single dash speaker hole. Are you sure you don't have speaker grilles off to each side?

I just bought a pair of Infinity Reference series 3032cf speakers for the Imperial.



The Imp had a pair of 3-1/2" speakers as well as a single 4x10 in the dash.

I also picked up a pair of Infinity Reference series 9632cf 6x9 speakers for the rear.

http://www.crutchfield.com/p_1089632CF/Infinity-Reference-9632cf.html


They're still in the boxes so I can't comment on how they sound.