Should the best systems sound almost identical?

Too many variables. Time of day, day of week, room acoustics, local seismic vibration characteristics, associated cabling, local power behavior, tube selection, CD treatments, etc.

Bad example - all Strads actually do sound the same. That's why the discerning music buff can identify the characteristic Strad sound on recordings by Heifetz, for example.

The plot thickens. From Wikipedia:

Controversy over Sound Quality

Above all, these instruments are famous for the quality of sound they produce. However, the many blind tests from 1817[6][7] to the present (as of 2006) have never found any difference in sound between Stradivari's violins and high-quality violins in comparable style of other makers and periods, nor has acoustic analysis.[8][9] In a particularly famous test on a BBC Radio 3 program in 1977, the violinists Isaac Stern and Pinchas Zukerman and the violin expert and dealer Charles Beare tried to distinguish among the "Chaconne" Stradivarius, a 1739 Guarneri del Gesú, an 1846 Vuillaume, and a 1976 British violin played behind a screen by a professional soloist. The two violinists were allowed to play all the instruments first. None of the listeners identified more than two of the four instruments. Two of the listeners identified the 20th-century violin as the Stradivarius.[10] Violinists and others have criticized these tests on various grounds such as that they are not double-blind (in most cases), the judges are often not experts, and the sounds of violins are hard to evaluate objectively and reproducibly.[9]

In a test in 2009, the British violinist Matthew Trusler played his 1711 Stradivarius, said to be worth two million U.S. dollars, and four modern violins made by the Swiss violin-maker Michael Rhonheimer. One of Rhonheimer's violins, made with wood that the Empa researcher Francis Schwarze had treated with fungi, received 90 of the 180 votes for the best tone, while the Stradivarius came in second with just 39 votes. The majority (113) of the listeners misidentified the winning violin as the Stradivarius.[11]

Analysis of the treated wood revealed a reduction in density, accompanied by relatively little change in the speed of sound. According to this analysis, treatment improves the sound radiation ratio to the level of cold-climate wood considered to have superior resonance.[12]

While the majority of world class soloist play violins by Antonio Stradivari, there are a few exceptions. For example violinist Christian Tetzlaff formerly played "a quite famous Strad", but switched to a violin made in 2002 by Stefan-Peter Greiner. He states that the listener cannot tell that his instrument is modern, and he regards it as excellent for Bach and better than a Stradivarius for "the big Romantic and 20th-century concertos."[13]