Dynavector DV20x2H cart for MM phono stage ?

I had the 20XH and 20XL and I tried them both with the whest 2.0 phono stage. It offers MM and MC at I believe 70DB gain. With either the L or H version I preferred the MC input. It has always sounded weak and light with the MM input. So I don't know if it's my phono stage that is the culprit or the 20XH would like to see more than 40DB gain I can't say but in any cart situation I've been in I like more gain than less. I really don't like putting my volume knob at 3pm on the dial if possible

"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.