Need advice on building an A/V system

Probably can't address all your questions, but I've recent experience from revamping my HT system. For me at least, a separate DAC seemed unnecessary given Oppo's highly touted units (I got the 103 and your 105 should be even better). I switched from an old AVR to separates and the difference is nothing short of amazing in terms of sound quality and "slam". Check out Marantz AV7005 and MM7055 combination. If you have more to spend, the higher priced Marantz should be at least as good or better and of course there are other good brands out there. I also added a musical 12" sub and a good line conditioner/surge protector. Look for close outs and sales. Good luck and cheers!!

Since you are all set for 2 channel, a receiver is the way I would go. There are plenty of good ones in your price range. I sell Sony, Yamaha, and Arcam. The Arcam being my favorite, and what I use at home.

With $3k, I'd be inclined to budget about a third each for AVR, 5 speakers, and a subwoofer (or two).

One such combo:

A pair of sealed SVS 10 inch subs
A Marantz or Integra AVR equipped with Audyssey xt 32 pro
5 Gallo A'Diva speakers

I'd add a Sony Blu Ray player at less than $100 to complete the system.

Provided that the AVR has sufficient power for the speakers you choose, I think any of the XT 32 equipped models represent the point of diminishing returs for AV electronics. Similarly, the dirt cheap Sony players provide a great picture and adequate + SQ so I'd save money there and use HDMI to access the higher quality DAC in the AVR. Subs and speakers will be more of a compromise on a $3 k budget, but the combo above should be very satisfying in most rooms.

The first place I'd allocate additional budget would be loudspeakers, followed by subs, followed by AVR, followed by BR player.

Just one more perspective for you to chew on.

Good Luck with the hunt

Marty