hi, new member here but i’ve been following this forum circle for months (half a year?) now. but it’s my first time to post

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after building a pair of OB-7 (i’ll post some pictures to share in a separate thread when i get a chance), my wife and i enjoy listening to music more than watching movies. i had to sell my 5.1 surround speakers (b&w 7 series) to fund the OB-7 project (+ servo sub) and i’m having no regrets so far. i’m still waiting on the servo plate amp to arrive but i’m starting to consider reconfiguring my audio system to bring out the best of the OB-7s and the servo sub, thus the reason for this post.
i prefer listening to music in 2-ch stereo but i still don’t know if that’s also the case for movies (sound quality over surround experience). but since i’m left with only a pair of speakers, i intend to replace my surround pre-pro and amp with a better system in playing music and maybe 2-ch movies within similar (used) price range. i won’t worry about the surround format decoding since i can let my PC decode and downmix to 2ch PCM.
currently i have a rotel rsp-1068 and a rotel rmb-1075, my first question would be the difference of the dac in the rotel and standalone dacs (e.g. dB Audio Labs, TriVista 21). the rotel’s dac is already hi-res but what other significant reasons can a dedicated dac provide over the rsp-1068 pre-pro? also, there’s no point in using a 5-ch amplifier driving stereo speakers, what amps out there that are significantly better at 2-ch reproduction and within the sub $1k range (preferrably used)? i’m open to building an amp kit as well if it will significantly reduce the cost without a hit in the performance.
i am in progress of my research and would appreciate any help, since the OB-7s will be one of my system’s core element i thought it’s fitting to ask here.
thanks and merry christmas!