Based on pedigree I'm sure the RME ADI-2 DAC FS could be an option if you want something that will last a very long time and does everything though costs a little (or a lot, its 959€ in Germany after all) more up front.
The other options (Topping DX7 Pro, Sabaj D5, SMSL M500) are certainly not bad either and can be significantly cheaper, you can find reviews for all of them here:
DX7 Pro:
https://www.audiosciencereview.com/...-dx7-pro-dac-and-headphone-amp-reviewed.9446/
D5:
https://www.audiosciencereview.com/...ew-and-measurements-of-sabaj-d5-dac-amp.8337/
M500:
https://www.audiosciencereview.com/forum/index.php?threads/smsl-m500-dac-and-hp-amp-review.9606/
ADI-2 FS:
https://www.audiosciencereview.com/...version-2-dac-and-headphone-amp-review.13379/
If you want separate units, there's a load of options.
A fairly cheap unbalanced DAC with good performance and features would be the Topping E30:
https://www.audiosciencereview.com/forum/index.php?threads/topping-e30-dac-review.12119/, but there are a bunch of other options with different feature sets and slightly different performance (Atom DAC, Donald DAC, SMSL Sanskrit MKII etc.)
Balanced options at around 250€ are the Soncoz LA-QDX1 (
https://www.audiosciencereview.com/forum/index.php?threads/soncoz-la-qxd1-balanced-dac-review.13459/ ) and the Schiit Modius (
https://www.audiosciencereview.com/forum/index.php?threads/schiit-modius-balanced-dac-review.13769/ ), both a bit light on features.
Then of course, it's always easy to spend more money. You can get even more performance, but there shouldn't really be an audible differences after that point.
Headphone amp options are also not in short supply.
Starts at 99$ (more if you import them of course) with the JDS Labs Atom (
https://www.audiosciencereview.com/...ents-of-new-jds-labs-atom-headphone-amp.5262/ ) and Schiit Magni Heresy (
https://www.audiosciencereview.com/...gni-3-and-heresy-headphone-amp-reviews.10311/ ), the Topping L30 wich should be available soon (and in Europe too) also looks very good:
https://www.audiosciencereview.com/...asurement-of-topping-l30-headphone-amp.14252/
Then there are Geshelli Archel2 Pro (unbalanced,
https://www.audiosciencereview.com/...hel2-headphone-amp-review-another-champ.9438/ ) and 2.5 Pro (balanced), the THX 789 (from drop.com,
https://www.audiosciencereview.com/...easurements-of-massdrop-thx-aaa-789-amp.5001/) and THX 887 (Monoprice,
https://www.audiosciencereview.com/...thx-887-balance-headphone-amp-new-champ.8942/), at 500€ there is the Topping A90 and so on.
Frankly, there are just loads of options. They are all audibly transparent and deliver enough power for your 1770 Pro. It's mainly about what you like or want or might need in the future.
It's how they say:
There is no best option, there is just whats best for you.