I've been using a phantom center for about 3+ years and have no desire to go back to an actual center myself. I've owned a few, and have heard many 5.1 set up's from Revel, Linn, B&W, Martin Logan etc. and have never thought the center disappeared, and even if optimally placed and you could get it to totally blend in... you can get the same result (better IMO) from a phantom center from the mains.
It's not like I hate center channels, but if you're not rich, you could put that money you didn't spend on a center and center amp and put it towards better mains or other gear to actually improve your sound.
Optimally set up for awesome 2-chan listening w/ the mains and your front end will be stellar. Then set up surrounds to fill out the rears and you'll have incredible 5.1 sound from 4.1 set up (I actually have a 6 speaker set up, but two are subs so it's still called 4.1).
W/ my previous Newforms and now the Alphas, the imaging is terribly sharp and creates a seamless sheet of sound that connects perfectly to my 65" screen. Wherever a sound's recorded, that's where it images. If it's dead center that's exactly where the sound comes from.
A lot of mid-fi 'home theater' people IMO don't have their mains set up right and so their 2 chan. imaging isn't good, and they use a center speaker as a 'gap filler'.
note- make sure if you've got a TV for DVD's -that the screen's behind the speakers so that big plastic screen isn't reflecting sound. I fold down a fat, fluffy, dark blanket over the screen when doing music to pretty much erase the set acousticly, but have no problems when it's up and I'm watching a movie.
If you're sitting drastically off center (and why would you be right?) or you have a very small screen for HT (again... why would you? Hard to imagine pairing a set of Alphas w/ a 27" set right? heh) then 'Yes' the center image would not line up perfectly w/ center.
But like in my HT... if you're way off center the screen's on an angle also, and though the center image is tied closer to the speaker you're nearer to, it still really ties to the screen suprisingly well... but really...
Leave those seats for the guests you like the least. hehe
Not to mention the speaker levels are all screwed up when you sit way off center whether you have a center chan or not since everyone rightly calibrates to a center seating point.
I'm hoping the DVD-A/SACD player I'm getting will downmix a phantom center or else I'll be 'forced' to get a center chan. and another amp, but some I've got to mess w/ at stores downmixed the center.
BTW... where's our damn amps hey!?! (wrong forum) hehe
Otherwise every DVD player or pre/pro will perfectly downmix the center to the mains, and really IMO... there's no better more seamless matching center chan. than 'none'. Panning and tonal shift is inherently perfect.
I assume since you seem to only listen to 5.1 that you're using a pre/pro or rec. to turn CD's into 5.1 w/ DLPII right? Or else you no longer listen to CD anymore???
You couldn't only listen to DVD-A/SACD right?
I find the current DVD-A/SACD selection to not have a hi-rez version of more than a few of the CD's I own. Personally I find DLPII slightly degrades the front end, so while it does work pretty well for what it does, I still never use it.
Anyway... often a 'matching center' as called by a speaker company uses maybe the same or similar drivers though the center speaker is almost never the exact same speaker as the mains (the not even close Martin Logan centers are a good example of 'not matching center chans.), and the center if usually horizontal which is only to fit above or under a TV not because it's sonically better like that.
GR's Diluceo/Criterion could work well (like Danny mentioned). That's one of the cool things about monitor style speakers -you can buy a matching 360 degree set. Personally I'd only buy 4 of them though. I expect the imaging on the main pair is awesome..., but an actual center would give you more cone impact and power handling. That'd be a plus in that sense so hard to call.
As for surrounds... my thoughts are that it's impossible really for even the exact same speaker to exactly match the main speakers.
What? That doesn't make sense... they're THE SAME?!?
Yeah, but your ears don't hear the same from the back as the front. The most obvious thing is that the highs are dulled if your ears cup away from the sound.
Listen to a kick ass pair of speakers, then turn around... it's not quite the same.
It's funny... I had exact matching speakers in the past. The first were mid-fi ones that were fairly dull.
It didn't matter that they matched... they just weren't very good.
I later moved to Newform 630 which are a bit tipped up bright on the highs. Using those as mains... the surrounds didn't come close to matching them -but I expected that.
I later put the 630's as rears, and got the larger/same driver 645's so again had 'matching' mains and surrounds, but as I said the 630's had a diff. tone than the 645's being behind my ears. You could easily hear it from the test tone on my pre/pro. Same tone in all the speakers, but the rears were not the same as the front.
The Alphas sound to me more correct on the highs, not dull or bright, and just as detailed if not more-so.
Placing the 645's behind as my current surrounds their tipped up highs are toned down and oddly enough they seem to match the Alphas better than they matched themselves.
Weird hey?
Also, kinda liked Danny seemed to be saying... the surround info is just so often subtle ambiance and effects (plus the ear thing I mentioned) that IMO the surrounds are really far less important than the mains.
For music IMO monopoles are the way to go IMO. Di/bipoles are great for splattering sound all over and making rain and crickets chirping sound 'filling', but if there's an acoustic guitar of vocals from behind, you don't want that splattered around IMO.
Also I have the surrounds just slightly behind the sides. This gets them the closest to where your ears can hear them the clearest, and just behind you enough that they actually sound like they're from behind not the sides and can pan back and forth as recorded.
So that's my take on the subject and what I do w/ my Alphas. Hope any of this crap helps. hehe