My 990's faceplate is about 1" behind a glass door; there's maybe 2" on each side, 3" back to a cardboard rear panel which was pushed out to the room wall behind it to make room for the cables (on account of this unit is almost too deep for its space), and 6" on top. When it's running the top is warm but not hot to the touch. If the heat is degrading my unit's performance it must be mighty subtle because it sounds fine to me.
With your fans (quiet, I hope) I don't think you'll have any problems.