need advise, which is the weakest link in my audio chain

I would suspect that you would prefer a warmer sounding amp.  Even if your speakers are not that efficient, in a small room you should be able to utilize a tube amp of modest power output.  I think something that runs EL84 tubes, or 6L6, or KT 66 tubes would sound good.  These are nice sounding tubes that can deliver warmth without sounding murky or too polite and lifeless.

I personally find that the amp makes a huge difference in the sound, much more so than the choice of linestage or source components (assuming these are decent choices).  

Lots of good advice above…

I would add few things to try:

1. This will cost nothing: Swap diffusion and absorption panels - place the absorbers on side walls and diffusers behind speakers. If possible. Reason - room is most likely too small to make effective use of diffusers at the first reflection points. 
2. Not familiar with you amplifier and pre, but I would try another amp and if possible another preamp with it. 
3. I had the CD6006 it’s not a bad player but it isn’t as good as you can make it sound by adding a good dac. I agree with others here.

Just my thoughts 
 

Poor OP opened a can of worms. I would alway start with the free options and work my way up the money scale. 10x10 you are in a cube and that is very difficult to overcome. Follow the advice of @audphile1 and play around with adjusting your room treatment possibly adding more. Nothing wrong with your transport, and you could audition a better DAC heck there are some really good DACs under $2000.00 on USAM used. 

To buttress some of the above thoughts and suggestions, trying different amps would also be my first thought. I am using an excellent, fairly expensive DAC (Aqua La Scala), and fine, very revealing speakers (Fink Team KIM –again, not cheap), and recently, I had a minor repair done on my integrated amp (Circle Labs A200), which I have been very happy with. I took the opportunity to try three different, high-quality integrated amps in my system, as my dealer was generous enough to allow me to do so.

The first was an Accuphase E-380, the second a Luxman L-509x, and finally a SoulNote A-2. The differences between the type of sound produced was easily discernible in each case, and I ultimately found that I preferred my A200 over all of them. But the important take-away is that system synergy always matters. I have no doubt that for other audiophiles, any of the three amps that I auditioned could be end-game components. But within the context of my system, and given my preferences (slightly warm, detailed but not clinical, etc.), they weren’t as satisfying overall as the A200 (which, by the way, costs far less than the E-380 and L-509x).

One can certainly glean useful insights from reviews and anecdotal reports, but unless the component in question is heard within the context of one’s own system, it is risky to take anything for granted.

Finally, these symptoms all strike me as being consistent with the character of the amp. Yes, they can be mitigated in other ways, but a different amp may well solve all of those issues on its own, and prove to be a more 'organic' solution.

- a bit forward sound

- sometime may a little dry/harsh sounding when source recording is poor

- lack of sweet top end

Quite likely your interconnects and power cords need replacing

But first, Mad Scientist Audio's Graphene Contact enhancer is amazing, and much cheaper than replacing anything until you apply it

hth