The 1900 Philadelphia census image for this family indicates that both Louis and Leonie were born in Belgium, that they were married in 1880, had been married 20 years, and had both emigrated in 1889 (so it's possible that Louis came over first, and the rest of the family joined him shortly after). Some of these details obviously conflict with your 1883 marriage record. Leonie is listed as having had 5 children, 4 still living (4 listed in the household). The 1900 household includes 3 boarders, Arthur "Cavenir" age 25, Pierre De Graffe age 52, and Jules C. Becca age 49, all born in Belgium.
A basic search of FamilySearch's Philadelphia Marriage Index (which starts in 1885) does not seem to include any entry for Louis or Leonie, although it does list daughters Louisa (m.1909) and Augusta (m.1911). The actual index microfilms are also browsable, year-by-year (with yearly alphabetical indexes for bride and groom surnames), which can help if surnames have been badly mangled in the electronic index. Ancestry.com has their own electronic version of this index, which may be more wild-card friendly than FamilySearch's.
FamilySearch's "Pennsylvania County Marriages" has records from most counties other than Philadelphia, also starting from 1885. Some marriages registered in Philadelphia actually occurred in one of the surrounding counties (Delaware, Montgomery, Bucks or Northampton) or even Camden, NJ. Do you know the family's religious affiliation (i.e., have you tried church records)?
Ancestry.com also has Pennsylvania death certificates from 1906-1963 (images), and a few other assorted records for this Staquet family, but nothing that appears to bear on the question at hand (although it may be worth noting that in the abstract of Alice (Staquet) Supiot's SSA file, her mother's maiden name was transcribed as "Leona Musbois").