Can I put receiver and CD player on top of my sub?

>>Just one more thing, while playing these components leave the subwoofer off.<<

Then why have the subwoofer? Enlighten me.

If you really want to set the receiver on top of the sub, then do it. I suggest that you try some simple (and cheap) isolation tricks to keep the vibrations from the sub from rattling your receiver.

First, try filling 4 zip-lock sandwich bags half full with sandbox sand. Set them on the sub and then set the receiver's feet right in the middle of the bags.
Next, get a larger zip-lock bag and fill it half full of sand and set it on top of the receiver. Tap on the top cover with your finger to see if makes anything but a dull thunk when struck. You might need more than one bag.

If you want better and are handy with a power tools, then buy some 3/4" MDF and make a 3 inch deep box about 1 inch larger on all sides than footprint of the receiver (if the receiver is 18" x 15" then make it 20" x 17"). Seal the four sides and corners with caulk so that the sand doesn't leak out. Fill the box with sand 2-1/4" deep. Make the top so that it has about an 1/8" gap on all sides and it "floats" on the sand. Use 4 large sorbothane feet on the bottom of the box.
Again, use the large zip-lock sand bag on the top of the receiver.

If you want better yet (but it isn't cheap), then invest in the Brightstar Air Mass that is the right size for your receiver.

Sorry to be a Nay-sayer, but if you are going to put your gear on top your sub, then I would say putting zip-lock bags filled with sand is dangerous at best. This is in your bedroom, right? Well, what happens if you accidentally spill one of the bags on the top, or knock it over. I'm sure we'll all agree that vibrations won't kill your cd player, they'll just interfere with the sound. Sand, on the otherhand...get that in your gear and you'll be pretty unhappy.

Judy426-

Your sarcasm detector is not functioning.

No. Not recommended.
Ideally speaking, some serious referrence speakers have their crossovers mounted outside, on a separate box. Why would you want to shake the mounts and other components of a CDplayer and other gear on top of a subwoofer.

If space is a must, then, try an isolation trick as many suggested above. If there is a choice, avoid this set up.