Dynavector DV20x2H cart for MM phono stage ?

Provided the gain is at least 40 dB or so you should be OK.

My friend uses it with the built in MM phono pre of a Rega Brio R and it sounds great.

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