Opinion on 5 vs 7 channel and mixing brand speaker

Hi all. First of all, thanks for all previous advice. Finally got my amps in. MC205 and pair of MC601 and a used marantz av8801 processor. Need your option on the speakers set.

1. 7 vs 5 channel. Does it make lot of difference. I am currently having 5 channel (PSB image t tower, center and bookshelf) powered by MC205.

2. Mixing high end brand and entry level brand speakers for theatre? Any opinion on this?

I am debating if I want to make it 7 channel, the main speaker will be Wilson Sasha 2 and rest PSB. Or upgrade the 5 speakers and keep 5.1 while Wilson Sasha will be dedicated for stereo.

I enjoy both stereo and movie. But I spend just a little more time listening than watching.

Thanks for opinion.
The center channel contains the majority of what you generally hear. Typically it is preferred to use like speakers accross the front. If your room is large you could do 7.1 however you would probably realize more from 5.1 with matched fronts.
Mixing rears in 5 or 7 channel theater is really no issue. However, you will notice if the front 3 don't match seamlessly.
Sell your front 3 PSB's and put that towards a Wilson Benesch Square for center? I'd rather have Great 5.1 than mediocre 7.1-my opinion.
Yes I agree with Elevick. I have B&W 600 series loudspeakers for the front mains and center and had the M-1 mini-theaters for the surrounds. But I just didn't care for their sterile metal sound. I sold them and went with a pair of Monitor Audio Bronze BR-1 reference monitors with that warmer timber sound. These two little guys never cease to amaze me. I'm driving them with 120 watts of pure Rotel power each even though they're rated at 70 watts max input RMS but no problem. They can handle it easily and the details these two speakers produce for either music or theater is nothing short of amazing. They are in your face speakers and the mid-range definition is outstanding. They look great in oak and built well.
Understand matching front 3 is important. I am having budget issue and also space.

Wilson Audio's center is huge and the price is way too much. I can afford only the Sasha 2. Even if I can afford the center channel, I am stuck with only 9 inch clearance to place the center channel.

Will it be the same if I am able to look for the smaller center that's less expensive with similar specs, in term of the figures like frequency respond, range, ohm, and etc? Does it work that way?
You might be better off without a center than a mismatched one. The Wilson's are soooo good that it might work? You could contact someone like speaker city or madisound and see if they can find the drivers and come up with something similar. They will be honest with you.
Try to go without a center channel. You must know how well your mains image for stereo, and those are excellent speakers. My setup is used for both music and HT. After a lot of listening, I eliminated the center channel. Our KEF Reference 107/2s image the front plane superbly, dialog is fully intelligible and tracks voices across the 100" projection screen. I use KEF Reference 102s for surrounds that seem entirely adequate and some flat KEF's on the back wall that I rarely fire up. Of course you need to tell your processor that there is no center channel so it can parcel it out appropriately to the front LR channels.

I would not mix brands of speakers.
My 2 cents worth is forget the center channel. If you watch older movies, I find sound coming out of one certain spot very annoying, would rather hear the sound out of two speakers. The rears don't really have to match, as they don't do all that much. I'm not sure 7.1 is all that big a deal either, 5.1 is quite adequate.
Synergy across the front is strongly suggested for intuitive reasons .

The rears and surrounds use signals that are "manufactured" "fill-in" soundtracks without that same sensitivity. Hence same brand synergy is still preferred (nice to have ) but by no means system critical (need to have)

Recorded material other than 2 channel is primarily a manufactured multichannel recording . The movie soundtrack expansion from 5.1 to 7.1 has additional subtle "surround" effects introduced that are certainly only a nice-to-have at best.

Sure... I have the AIX pure PCM 7.1 format recordings showcasing that "sitting with the musicians" experience that has that initial demo listening interest.
The cold hard facts are that even this "pure" 7.1 audio performance provided by my ARCAM Bluray player feeding a separate high end 7.1 AV preamp/ precessor (driven by high end separate amps) still gets totally smoked by the performance provided by my high-end 2 channel CDP and integrated
The differences are not subtle.

Your takeaway:

Most BluRay concerts are only 5.1 in alternate CODEC formats.
Cable and satellite TV are still 5.1
Movie soundtracks are either 5.1 or 7.1 .... The latter "expanded format" still gets played on a 5.1 system; and whether you feel that you actually missing out on something is limited to a very small subtle esoteric difference that is a heavily biased anecdotal personal value judgement at best

7.1 is only a nice-to-have feature , not a mission critical feature.
IMO, 7.1 is much more desirable than simply nice to have. You don't hear of many users reverting back to 5.1. The 5.1 to 7.1 matrixing software continues to improve as do the 7.1 mastering technics.

When I first went to 7.1 the shortcomings of the dipole speaker were glaring in my room. Depending on the dipole design your not depending on a back or side wall reflection for the rear channels. With discrete rear channel speakers aimed at the listening field the room correction timing is more controlled which can be very beneficial for irregular shaped rooms. locating the side speakers requires the most trial and error to taste. I've had good results using "Master Commander" bulray.

If your lucky enough to have a large HT room evenly spaced speakers require much less room correction if at all. In this scenario the benefit of matching speakers can be more evident.

Analog two channel always has a more relaxed presentation then even the best digitally converted source material I've heard. Adding more conversions as with home theater is simply brutal to me. This could be a good reason to get the most from the source material with high quality playback components. I've installed seven HT systems for family and friends of varying budgets. For the last three I used seven $98 Pioneer SB-C22s and focused on better subwoofers with great results and satisfaction.

Its just TV,