Please clarify what you meant by "they are close - up to 1ft...., and when you say 90 dB and 75 dB for movies/music, do you mean the average spl, or peak (max peak you would have in movies and music)?
THX standard says for movies, allow 20 dB headroom for peaks, for music, 6 dB peaks are quite common, 12 dB are not uncommon, 20 dB's are rare, depending on the genre. If you are not sure, then I would give you an answer cased on a 20 dB peak allowance.
Online calculators normally calculate based on 1 speaker. The one ADTG linked let you input the number of speakers. You may be 3 dB more spl if two speakers are playing, but it depends on your room, speakers, so in my opinion, it is better just assume one speaker first and go from there.
While those "most guys" are right in a general sense, it "REALLY" depends on the individual's setup, for argument sake, any mid range AVR, even the light weight AVR-X3500H can drive 4 ohm or even 2 ohm speakers, depending on each individual's conditions.
Sorry about the long answer, but there are no much hearsay on the internet, it is hard to counter so many misconceptions and confusing information with a one liner.
As soon as you provide the clarification on the "....1ft...." and whether you desired spl are average or peaks, I can use my spreadsheet calculator to give you a good idea whether you AVR is struggling. For now, suffice to say, they might have been, but it depends, yes "REALLY"..