Dynavector DV20x2H cart for MM phono stage ?

"Can I use a preamp with MM phono stage for this cart?"

Unless you have an exception like Ejlif and his Whest, you will need to use a MM phono stage. Otherwise, you will almost certainly get a lot of distortion. Being able to use a MM phono pre, in your situation, is a good thing. The less gain you need from the phono stage, the easier it is to get one at a lower price that sounds good.

Any good suggestion for preamp in my case? I have parasound A21 amp and Thiel CS2.4. My budget is ~ 2500.00

For that amount you could get a pretty great phono stage that should offer both MC and MM inputs and you can see what works best for that cart. You will also not be locked into only playing with MM carts, you could upgrade to the even the next step up in the Dynavector line the 17D which in my opinion is a lot better than the 20XH. The 20XL is even a noticeable imporvement on the 20XH at least it was for me. How about the Parasound JC3 phono stage? Looks like you are already a fan of Parasound products.

I think spending $2500 for a Phono pre with your TT is way over kill...You should look at a Musical Surroundings NOVA II. It is super quiet and will work very well. It costs around 1200 new.

What line stage are you currently using? Also, I agree with Ejlif. If you have $2500 to spend on a phono pre, it would make a lot of sense to go with a low output cart. I haven't heard the 17D but I have the low output version of your cart and its a very nice upgrade over the HO version.