MMGs flat with Complex Music

System sounds absolutely fantastic (very smooth, great soundstage, very detailed, and all the other good words reviewers use) with vocals and other non-complex music (like a trio or a small group). However, with a symphony orchestra, it just sounds flat. Almost like it is a different system. Don’t see how the electronics could be an issue: Naim CD5, Conrad Johnson PV12 tube pre, Conrad Johnson MF2500 (250 wpc, rms, both channels driven). Anybody have a similar experience? Am I asking too much from the MMGs? I really like the Maggie sound. Do I need to upgrade to bigger Maggies? Which ones?