I agree with Rives, and know several people who have gone from using a center channel to phantom center mode and prefer the latter.
To widen the listening area in phantom center mode, you might try this: Toe your left and right main speakers in severely so that their axes actually criss-cross a little ways front of the center listening position. Now for listeners off to one side of center, they are more on-axis of the far speaker and way off-axis of the near speaker. Since most speakers are somewhat directional (especially in the upper treble), the far speaker will be a bit louder than the near speaker which will tend to offset the latter's earlier arrival time. The result is good soundstaging over a much wider area than you'd have with main speakers pointed straight ahead (or only toed in a little) in phantom center mode. You may have to experiment around a bit to find the optimum speaker separation and toe-in angle to give good center-fill from well off-axis.
This may not work with all speakers but it doesn't cost anything to try, and will almost certainly sound better than a system with a mismatched center channel.
To widen the listening area in phantom center mode, you might try this: Toe your left and right main speakers in severely so that their axes actually criss-cross a little ways front of the center listening position. Now for listeners off to one side of center, they are more on-axis of the far speaker and way off-axis of the near speaker. Since most speakers are somewhat directional (especially in the upper treble), the far speaker will be a bit louder than the near speaker which will tend to offset the latter's earlier arrival time. The result is good soundstaging over a much wider area than you'd have with main speakers pointed straight ahead (or only toed in a little) in phantom center mode. You may have to experiment around a bit to find the optimum speaker separation and toe-in angle to give good center-fill from well off-axis.
This may not work with all speakers but it doesn't cost anything to try, and will almost certainly sound better than a system with a mismatched center channel.