Magnepan MG-12s coupled with A/V receiver

I recently purchased a pair of Magnepan MG-12s, and took them home and plugged them into my also newly acquired Pioneer 1019 A/V receiver. The sound is not what I heard out of the Maggies at the dealer. I am wondering if I have the wrong receiver and would like some advice on a replacement. The Pio does not have a pre-amp output (except for a sub), so I cannot utilize an amp with it. I am new at pursuing good home audio, and would appreciate any advice. I am mostly interested in good music quality, but it will also need to run my TV sound. Thanks, Mark