Realistic is terrible in my opinion with THD ratings ranging from .9% to .5% in the late seventies to the mid 80's and costing upwards of $500, while a comparably priced receiver from any real company was able to pull off .1% THD or better at that time.
Your opinion doesn't match my observations. In the first place, most of those Realistic brand receivers were made by the Japanese majors under contract and used similar circuitry to what the manufacturers put in their own brands. The build quality of the ones I've had apart, including some of the earlier models made by Foster (parent of Fostex), is generally competitive with facing models from the Japanese majors. In the second place, the correlation between THD and listening quality is somewhere between weak and nonexistent, so it doesn't make much sense to use a THD number as a figure of merit. THD and IM graphs showing the level and order of the distortion are more useful, but I don't know of any manufacturer that publishes those graphs in its spec sheets.