Pro 800 is a Behringer's attempt to knock off Prophet 600. I had P 600 in my studio 12 years ago, for almost a year, and I loved it.
That being said, NOTHING comes close to Prophet 10 sound.
On top of the behemoth oscillators and lush filters, we got new features like Stack/Split, Poly-unison, q compensation, velocity and aftertouch amount per patch... All this gives you one of the most seminal synths in the history, with both filters found in older revisions, plus all these new features.
While Pro 800 is decent sounding from what I hear online, if you want a Prophet, keep it. There is no clone, direct or indirect, that can sound like it. The only synth that sounded like my Prophet 10 was Prophet 5 REV3 I had ten years ago or so. I had Prophet 600, 08, 12, Poly Evolver and now I have REV2, OB6, and none of these synths can sound like P5/10. Sure, there are patches that can be similar, just like there are patches P10 can't do (compared to REV2 specifically, due to the different architecture). REV2 is made to be a workhorse and modulation monster, Prophet 5/10 is immediate power and sound that cannot be matched.