Where is the weak chain in my system?

First,try putting a tube pre in line with the dac. Second, Audio Research to me is not what I call a warm sounding amp. Yes very detailed and musical. I have also found that VAC amps have a very smooth presentation. If you can find them in a mono design the better. Second try different cables. The crosslinks are good but are limiting what your equipment can do.

On paper you have put together a very high quality system and it's not surprising that you should like the basic sound. I suggest that rather than wholesale changes of equipment you concentrate on careful system setup. Warmth is a quality associated with the upper bass thru lower mid-range (say, 100 to 300 Hz). Speaker and listner position can greatly influence the relative perception of this frequency band. Your equipment stand and any coupling/decoupling devices are also critical. At the level of equipment you have a high quality stand (Polycrystal, Solid Steel, etc.) is critical. The relative lack of smoothness you refer to could be due to either hard surfaces near the speaker generating high levels of sound reflections, or problems with your recordings. Hard sounding recordings are problematic, but speaker reflections can be dealt with via acoustic treatment.

Cardas makes good quality cables at fairly reasonable prices and you might want to consider upgrading your speaker cables. It's been my experience that using a single brand of cables has synergistic effects. Good luck!

If your preferences run to warmth and smoothness, I would second Bozo's recommendation that you try a tube preamp. That may also give you the power you seek. Start by auditioning something which is neutral tube-y like a CAT. If that doesn't pull your chain try something more 'romantic' like a Cary.
P.S.Do you have wall-to-wall carpeting with a pad? That makes a huge difference!

I would say the weakness if not bottleneck in your very nice system is the Crosslink. Beyond going up the Cardas line I do know of a good recommendation. An upgrade to thicker cable like Cross, Golden Cross or Hexlink would definately be a smooth move. Maybe some sort of power treatment would yield benefits as well. I'm just getting in to the power game, so i have no firsthand recommendations. i have heard good things about Audio Prism's quietlines, PS Audio powerplants and Monster's HTS-2000.