Alexei could well join the legion of Alex names popular in the US. There are countless opportunities to exoticize Alexander, and Alexei is one of the most straightforward. Other variations are: ALEXANDROS, ALEXIOS, and ALEKSEI.
Alexei Alexeyevich Abrikosov, Soviet and Russian theoretical physicist and Nobel prize winner
Alexei Romanov (1904-1918), the only son to the last czar of Russia
Alexei Ramirez, Cuban Major League Baseball second baseman and shortstop for the Chicago White Sox