This has eliminated the vibrational problems I had before, however now I'm seeking to eliminate the spinning noise that these drives emit.
There are only 3 real choices for reducing "airborne" noise such as a fan or a spinning platter - in no particular order, and "dumbed down" (so the message gets across even if I am not 100% technically correct).
(1) Have the source of noise further away.
(2) Deflect the noise.
(3) Dampen (absorb) the noise.
1, is obvious.
2, is essentially what the sides of a case does, the noise bounces around until it finds a way out, but in doing so causes other things (e.g. case sides) to make noise themselves, which is why an aluminium side panel sounds worse than a steel side panel - aluminium is more resonant than steel. Also this is why cases that dont have direct exposure to the inside are quieter than ones covered in fan holes (P180 series for example), the noise essentially bounces around until it looses its energy without much of it escaping.
3, Foam materials, or bitumen sheets or similar, or even the side panels of some Antec cases (P180 series, Solo etc) have double/triple layered sides to absorb the sound.
Sadly it sounds as though you dont have the space to add foam or other layering's to deflect or absorb the sound, so your only choices are to swap case (expensive and a pain in the arse), or to move the PC or perhaps to put something in-front of it as a direct block between the PC and your ears, a sheet of board would do a great job to just test with if you have a spare bit around the house.