Home theater help from scratch 5.2 25k budget

The center channel is really only needed in theater situations where a lot of people are sitting off center. Anyone seated on line with the center, or close to it, will hear the soundstage which will sound like there is a center channel even when there isn't. Since hardly anyone has a home theater with 20 people sitting well off-axis this is a good example of the industry selling people something they simply do not need.

Whether or not you need surround speakers depends on how important it is that you have the whizz bang effects going off behind you as compared to a really good and compelling soundstage all across the room in front of you. Because you cannot have both. No HT gear made, and certainly not the Rotel/Arcam stuff you're looking at, will do that anywhere near what you can get for the same money with plain old stereo.

Listen for yourself and see what I mean. If you are gonna throw that much money away on HT marketing at least go into it with your eyes - and ears - open.

You might get better responses posing these questions in a forum focused on home theater, like AVSforum.

I'll share some of my thoughts on home theater.

Get separates - separate amp(s) and pre-pro.  Sound quality should be better and a good amp(s) will last a long time.  The features and video and audio formats change or get upgraded so often that pre-pros become obsolete quickly and lose their resale value even faster.  

SVS is a good choice for home theater subs.  So are Rythmik and PSA.  You can often find good deals on used subs, around 50% from buying new.  In my experience, subs have been pretty reliable.  All but two of the 8 that I currently own were purchased second hand and all are still going strong.  The ported subs you chose will have more output than their sealed equivalents and are a good choice.

Your mains and center channel are more important than the surround speakers, allocate your budget accordingly.  If you are putting together a surround system, the center channel is where almost all the dialog comes from.  

I'm not familiar with the speakers you mentioned.  I'm using Harbeth Super HL5 Plus speakers as my mains.  Not sure if they'd fit in your space, but they aren't very big and can play loud.  My system is focused more on music, but the Harbeths do great with movies.

Don't go to Best Buy to audition equipment or get advice.  If you mention where you live, other posters might be able to offer advice on reputable dealers you can visit.

Fwiw, for that amount of $$$ you can build one heck of a great HT. I'm in the seperates camp. I suggest you look into "demo" gear from authorized dealers.
Full warranty comes with this type of purchase. I highly recommend tonality matched speakers, a upscale processor, upscale amplifier and a decent source component.
For comparison my HT is 23x15x8 5.1 no atmos wanted
Processor Acurus Act4 @4800 "demo" SRP 7900
Speakers B&W 803d2 front @6000 SRP 12000 "demo", B&W center @350 SRP 800, Polk rear 500 vintage SRP 450 JL F112 v2 Sub @2700 SRP 3700"demo"
Amp Emotiva Gen3 5Ch @1900 new (the Krell died unexpectedly )
Oppo 103 @459, Hitachi 65" 4k flat screen @ 579
Assorted cabling approx 4500 to 5000 all purchased used
Total HT cost 22238 approximately on the high side, does not include room treatment or aesthetics. 

It totally is the cats meow which I enjoy daily for both movies and music.
Shop wisely and never ever pay SRP.

Monitor Audio Platinum and Anthem HT receiver.