A guru is an influential teacher or a popular expert, so certainly anyone with enough AV knowledge could be called a guru. It's obviously a self-chosen moniker meant to be memorable for marketing terms, but also is quite applicable to the situation. Certainly when it comes to front projection, in many areas I would be considered a 'guru' since I have over twenty years of experience working with front projection and care about the subject matter.
Some of my biggest considerations in a room like the OP is dealing with are to ensure that you build in pathways to add/remove/adjust things in the future. In my theater with relatively low 8-foot ceilings, I will be putting in a soffit around the space which will allow for cabling access to the walls and ceilings throughout the entire theater space at any point in the future as I need it. Something like a soffit provides a nifty way to add some nice indirect lighting to a theater, while adding the capability of adding functionality in the future as needed.
A space for the audio components needs to be decided upon up front and should not be within the theater space itself. So, plan on all equipment NOT being in the room and just using a quality universal remote control. Plan the cabling runs so that additional wiring can be added/removed in the future as need be. This is especially true for the HDMI cable which we have seen jump from a sub 3Gb/s connection to a 48Gb/s connection in the last decade or so. Cables will change, and you want to be on the front of that change, or at least be able to adopt to the change as it comes along.
If you build a room that can accommodate change, then you don't have to build a room that is beyond what it needs to be today. Maybe the goal is that $500,000 Ferrari room, but if the budget is $50K or whatever, then you have to build the room that the budget allows, and you shouldn't overspend for things you may not actually need or afford at this time. A proper 7.1.4 setup is a good starting point, but your budget does afford you to get into a 9.2.6 system (or better) without it being a huge strain to the budget.
I would personally be hard pressed not to do an acoustically transparent screen in such a room, which adds some planning. Especially if there is a false wall being added to the setup. As well, you have to consider screen size and a projector up front so you're prepared for that singular significant hit. Something like a JVC RS4100 may set you back $25,000, but may well be the appropriate projector for that space. Add a decent AT screen to the setup and you may be in $30,000 on the video portion by itself.
Anthem certainly has some very solid gear that makes a lot of sense for the money. You quickly get into the uber expensive when you look at brands like Trinnov that can run well over $15,000 for just the audio processing. That's not unreasonable if that's your goal and direction, but it may be more than you want to address for this part of your home. Especially when you really will want to have proper acoustical treatments in the space along with very solid speakers throughout. So, stepping down to a Anthem from a Trinnov is a huge price difference, but not necessarily a huge quality difference. An MRX 1140 from Anthem will give you 15 channels of processing power at $4,200. Not bad at all. The question would be that if something like the AVM 90 (pre-pro only) at $7,500 would make more sense or not and if that's money well spent. Or if it is worth upping the budget for something like that.
NOTE: I find that home theater lighting is one of the MOST significantly screwed up things that people get wrong. This is often addressed by good home theater companies, but it is often VERY late in the game that it is brought up.
MINIMUM: Each row of seating needs a row of directional (spotlights) placed above them. Each row needs to be on a dedicated dimmer. This way lighting towards the back of the room can be brought up 'brighter' while middle or front rows can be off or dimmer. It allows for movement in the room, without flooding the room with lighting and seriously impacting the on-screen image. There also needs to be about TWICE as many lights in a theater as a normal family room. Flood lights should be in the space for general entry/exit from the room and to provide plenty of lighting for cleaning and working on the room when those lights are brought up to full power. Dimming 20 lights is easy. Adding more lights when you NEED 20 lights sucks to deal with. So, make sure there is plenty of BRIGHT lighting in the room to deal with the dark carpet, dark walls, and dark ceiling. For God's sake! It is a theater, don't dress it up like another family room. Dark, dark, dark, dark, dark!!!
I don't go overly deep into the speaker well. There are tons of excellent speakers at tons of price points. But, it is rather easy to drop $10,000 a speaker and be convinced that is the right thing to do. I'm a fan of the Meridian DSP8000 speakers... their current XE model is $125,000 a pair. So, yeah, quick and easy to blow budget.
