Rubidium Clock

Can anyone advise whether an Esoteric Rubidium clock would improve the sound on my Esoteric X-01/D2 player? I have been told "not much since it is a one box." But the reviews have seemed to indicate that the upgrade in sound quality is quite apparent. I am aware that some upgrades are very small in their ability to be heard, others are like a whole new piece of gear.
Any advice is appreciated.
Yes, I'm looking to add a external clock to the D1s and then output the clock signal from the D1 to the RedNet D16.
BTW, the RedNet is the real deal, just replaced my USB set up and was amazed of the immediate improvement in SQ, worth every pennies in my opinion. 
Next up, will trying out some of AQ crazy priced CAT6 cables.

ysound - I'll second your recommendation of the RedNet. I also have a D16 and love it.

Zephyr - the Cybershaft is going into an Antelope Liveclock which is then feeding the above mentioned RedNet D16 and a Mutec MC-3+ USB reclocker. I've been very pleased with the outcome.

Interesting discussion. I'm using Oscilloquartz 8607 powered by custom PSU and very happy with results in my Aurender/dcs system. Problem now is availability of 8607 on used market so your option could be very interesting alternative
That looks to be one outstanding OCXO clock module...phase noise and precision specs are really impressive! It reports discontinued unfortunately....this seems to happen alot from what I've seen recently.  I'm told that vendors often will buy up 1500-2000+ units of such a component when they find it and test it/validate its quality just in case. Very similar to what happened alot in the DAC chip market and how some vendors (AMR, others) have chosen to proceed (which is a good approach IMHO).....