A few questions:
1) The R8a's seem exorbitantly priced for surrounds. They appear to be the obvious match, but any suggestions for acceptable alternatives? The KEF in-wall options with Q drivers seem like a much more affordable possibility. Thoughts?
2) Any views on the capabilities of the 12b sub for this application? I appreciate the aesthetic appeal of brand matching, but I have had positive experience with the similarly-priced SVS SB2000.
3) Would it be worth considering additional investment for the R400b sub? The smaller footprint is very appealing, but not sure what to think about the twin 9" drivers. Any experience with this sub in a similar setup?
4) My preference for the separates is based on my understanding that the R's can be demanding from an amplification perspective. I'm prepared to spend the money for separates if this is actually true. Any experience using a single box (e.g. higher range Denon) to comfortably drive a similar configuration? Any suggestions for alternatives to the Marantz separates? I've had positive experience with the Marantz/Denon sound for HT applications, but I'm open to other ideas.
Thanks to everyone in advance - this forum has been a great learning resource.
1) In terms of the R8a's the price looks to be mostly due to the matching finish of the R series. I use the cheaper Q50a's personally in my setup which retain the same angled cabinet shape if you're wall mounting these for surrounds. If you're not wall mounting, you can easily go with cheaper bookshelves like the Q350 on stands. Also as an option, you can try and track down the now discontinued R50's which have been replaced by the R8a earlier this year, whether it be through your dealer or the used market.
2/3) Although I personally haven't tested them in home, I've researched the 12b & R400b as potential options in the past 6 months for my living room setup for the nice finish and smaller footprint. Going by reviews and measurements though, these subs just don't stack up to the other internet direct companies subs like most here will tell you when it comes to performance and pricing.
4) The need/usefulness of seperates will definitely depend on your volume and listening habits. If you're going to get one of the higher end Marantz/Denon units, they may be perfectly sufficient for your needs. I have always used bookshelves and never ran full towers before though, so in that application maybe someone with better knowledge can chime in. If seperates are the way to go - then it would allow you to just stick with the AVR that has the necessary processing channels that you need (7,9,11,etc.), and not worry so much about going for the highest powered unit. I will mention in regard to Denon models, I know they are currently rolling out the 2019 models, so you may be able to save some of your budget with a 2018 model on closeout pricing or something... again that would be dealer specific.
As much as I like my SB-2000 sub musically, it does lack punch for HT. There are some very good hybrid subs on the market that can give you the best of both worlds.
Like pase22 says, there's a really good selection of subs, especially if you're located in the US and don't have to worry about crazy shipping costs and customs fees. Most people will recommend ported subs for your application, and multiple of them. It will mainly come down to your budget, and if other things matter like the size/finish/footprint of the cabinet then you might want a sealed option. For example, because I have a living room setup, and want to move my sub placement to the front soundstage - I have been specifically looking for a smaller footprint sub with a nice finish to match my KEF R300/600c combo. I was pretty set on the SVS SB3000 (since I am in Canada all the other sub companies I contacted for final to the door pricing were crazy)... but with luck I came across someone with a used ad selling his 2 HSU ULS-15 mk2's, and I will be picking one of those up today! It allows me to move up to a 15" driver with a decent looking box that's a smaller footprint than my current ported model.