Stacking gear no more rack space does it affect sound quality

It may or may not affect the sound, but I would worry more about making sure everything has sufficient ventilation for proper heat dissipation. You wouldn't think digital components generate much heat, but I recall my Oppo 205 running quite warm and I would hesitate to stack anything on top. 

Stacking is very bad for sound get a bigger rack asap.

That is a place you can make a LOT or get rid of a LOT of noise.

# 1 Placement. Be careful what goes where. 

Turntables/Tape units, valve gear (PtP), and digital gear don't always play well together.

# 2 Shielding and cable routing only ADD to the noise issue or detract from it. I call it "Cable Art" I like cabling to look nice and be QUIET.

Three things are left in my mind. 

# 1 How easy is it to access the gear for playback and cleaning?

# 2 How HARD/EASY is the access to input/output panel (s) and or to SWAP gear and cabling?

# 3 WHAT kind of a mess am I LOOKING at.. Looks count.

BUT then I look in the mirror.  Maybe not so much. :-)

Gear racks use to be all the rage.. They still are in a practical application, BUT who says stereo guys are practical. 

20k gear racks just touch the tip of stereo-nut-ism. I know of NO CURE!

Besides treatment cost money, that could be spent on stereo STUFF..

I say feed the BEAST..

Regards

I agree with rodman EMI/RFI and ebm. I do have a couple items stacked, but not more than 2 high for sure. Heat is a problem for electronics reliability, try to keep them cool.

I would be most concerned about heat dissipation of the unit having another one stacked on it.