IIRC Rheem used to be re-badged Palomas, but may have switched recently (to Takagi?).
If you have any distance to go with the exhaust venting, you may be better off going with a condensing version. The unit may cost considerably more, but PVC venting is far cheaper than stainless, and A: the installed cost may be lower and B: the avaibable tax & rebate subsidies may be higher.
Unless you take your incoming water directly at the outflow of a glacier, or are running a monster of a shower with deluge-sidesprays a 199K burner is likely going to be overkill. Sure you really need it? What are your incoming temps and flow rates like?
If you heat your house with a hydronic boiler(force hot water baseboards/radiators/radiant floor) you may get as-good or better efficiency, and noticably BETTER flow performance with an indirect-fired tank running off the boiler than with an 0.84 EF tankless, for a lower installed price (also subsidized.)