Well--I'm going to offer a completely different opinion here. If the priority is 2 channel listening and it's typically used as an HT for 1 or 2 people, use a phantom center, where the center channel is divided amoungst the mains.
Here are the advantages:
1. Less expensive
2. No speaker in the middle that corrupts your 2 channel performance
3. No issues with timber matching mains to center and getting the tweeter height of the center the same as the mains. With a good 2 channel (mains) set up this can sometimes be a more seamless soundstage than when using a center speaker.
Here are the disadvantages
1. Your mains have to work harder--they have to do the work of the center speaker. For movies this is often 70% of the sound, but your mains are porbably much higher quality than you would have for a center--so this works in a way. It is possible you won't be able to achieve the volume that you want if your mains have to work too hard--but this is room and speaker dependent.
2. If you seat many people and they get off axis, the dialog will not appear to be coming from the center without a center speaker.
I own Martin Logan mains. I have the Martin Logan Logos center channel. Given my current configuration--the logos is in the box, not being used, and I don't miss it a bit. I am close to not having enough power on the front soundstage and could use a center just to achieve higher levels, but I don't listen at THX volumes (I need my ears long term).
Here are the advantages:
1. Less expensive
2. No speaker in the middle that corrupts your 2 channel performance
3. No issues with timber matching mains to center and getting the tweeter height of the center the same as the mains. With a good 2 channel (mains) set up this can sometimes be a more seamless soundstage than when using a center speaker.
Here are the disadvantages
1. Your mains have to work harder--they have to do the work of the center speaker. For movies this is often 70% of the sound, but your mains are porbably much higher quality than you would have for a center--so this works in a way. It is possible you won't be able to achieve the volume that you want if your mains have to work too hard--but this is room and speaker dependent.
2. If you seat many people and they get off axis, the dialog will not appear to be coming from the center without a center speaker.
I own Martin Logan mains. I have the Martin Logan Logos center channel. Given my current configuration--the logos is in the box, not being used, and I don't miss it a bit. I am close to not having enough power on the front soundstage and could use a center just to achieve higher levels, but I don't listen at THX volumes (I need my ears long term).