Revel f208, dead center image but everything jumbled up?

Reverse the polarity on one speaker and see if that helps! 

It might be helpful if you tell us what components you are using with these speakers.

How much toe-in are you using?
Revel F208/206 recommend direct aim/toe-in at the listening position for best focus of soundstage, incremental degrees of away from direct aim to widen the soundstage.

The complaints I hear from the performa 3 line is usually pinpoint imaging but no real sound stage. Try putting them within a foot of the wall behind them to help with bass.Revel prides themselves in wide dispersion designs so maybe some treatments at first reflection points? 

The image is pretty dead center which is great and I like the vocals, it’s lifelike. The bass is pretty good as well as the HF. However, since the image is dead center, I am not feeling the sound stage. It feels like drummer, vocalist, bassists are all jumbled up or in the same straight line. It doesn’t even feel like the sound is coming from the speakers,

This is actually what you want. Not the jumbled up part, but we can talk about that. But the lifelike vocals, bass and HF being good, and the sound not coming from the speakers. That is exactly what you want. The better everything gets the less and less anything appears to be coming from the speakers, ever.

So now before you jump to conclusions and start messing around too much let's stop and listen carefully and think about what is really going on here. 

When you say "jumbled up" what exactly do you mean by that? In audiophile lexicon we have a lot of visual metaphors for sound but jumbled up isn't familiar to me. What you want to hear is the sound of each instrument and singer is so clearly rendered you can hear its full timbral and harmonic character, and not only that but the acoustic space in which it was recorded, and not only that but this is all rendered in a palpably believable way such that you feel you are there in the recording space with them- AND it maintains all these qualities even when they are all playing together at the same time and loud. 

This is what I have in my room and this is what I have always in my room regardless of it being a stereo or mono record. The only difference is with mono this is all coming from a sort of spherical area centered between the speakers. It would probably be more of a point but when the acoustic is captured really well it is almost impossible for it to ever sound like just a point. 

So now, the think about it part. You have a good solid center image? That is not all that hard to achieve. IF the speakers are PRECISELY equidistant and symmetrical - not within a few inches, not within a half an inch, not within a quarter of an inch- PRECISELY equidistant and symmetrical- AND they are out a few feet from side walls, THEN we need to think about what exactly you are hearing on different recordings. My hunch is your speakers and everything else are fine, you simply are not used to hearing quality imaging.

Not all recordings feature a wide expansive sound stage. A lot of recordings are pure crap. Streaming and digital are pretty crappy, but not quite so crappy you hear everything jumbled in the center.

I would suggest a  recording known to have a nice wide deep sound stage. Roxy Music Avalon, Jennifer Warnes Famous Blue Raincoat, Tom Petty Southern Accents. If you are listening to the Stones and the sound is all jumbled up in the center, relax. Try a few good recordings and get back to me.