Assuming that this is dual purpose (for 2 channel music and HT use), I'd really look for wide dispersion speakers all the way around. I'd also go 7.2 channel because - my guess is - this is a big enough space to justify that. This could be omnidirectional (like Ohm) or just a very wide dispersion design (like Gallo). A pair of Ohm 3000, a matching center and 4 on-wall surrounds would run (IIRC) app. $10K.
A pair of Gallo Ref 3.5 plus a matching center and 4 on-wall Strata surrounds would probably run about $1k less (unlike Ohm, you can sometimes find these discounted and you might come in even lower with Gallo).
A pair of excellent 12" sealed box subwoofers from either Rythmik or SVS would run a bit under. $1500.
Either way, call the speaker side of the equation $11K. (If you go 5.2, it'll save $2 to $3 k, depending on the brand.)
Since I'd personally use HDMI and decode audio in the pre-pro (rather than the player) I'd ignore the BRP's audio capability and buy the least expensive Blue Ray player whose video performance I like (and most are very very good, IMHO).
The dirt cheap ($100) Sony blue ray players produce IMHO excellent images (and I'd personally save the $ and go that way), but that may offend some sensibilities. I understand that the $1200ish Oppo BR players are highly regarded by many here and they have a more appropriate "pedigree", if that's important to you .
Let's say that that leaves +/- $8K for a pre-pro and multi-channel amp.
I'm a fan of Onkyo/Integra pre-pros ($1500 - $2500), but you could also check out the Anthem D2 which is more expensive but highly regarded. Any sufficiently high powered solid state amplification will work well with either set of speakers and I'd probably choose a multi-channel amp from the same manufacturer as the pre-pro so that the units' appearance matches.
Any of these combos should be comfortably within your stated budget and I think any of these set-ups will produce really good sound for 2 channel use in your large space, as well as excellent, uniform coverage for HT use.