As already mentioned, go with a Accushot Atlas bipod with AMD or Larue lever mount...I have Harris, GG&G , Tango down . This bipod is the best by far
Your biggest investment will obviously be a good scope. Lots of good choices out there on the market. All depends how much you want to spend
As far as scope mount, if you plan to leave your optics on the DMR rifle then go with one piece from AMD Recon or Larue SPR/M4 . Both these are cantilever mount for ARs
Another option is if you are also using scope for bolt gun is to use Badger ( or comparable rings ) on a cantilever riser adapter
For example, i use this scope on one of my bolt guns during hunting season
Looks a bit ghetto, but actually stiffer than the Larue SPR/M4
Not sure what you are planning to load ( 69gr SMK , 77gr SMK ...duplicate of Mk262 load , 75Gr A-Max )
The load I find that shoots the best out of all my SPR / DMR type is the 75Gr A-Max but they are single load only
If you haven't bought dies yet you should look at the Redding competition bushing dies and a Redding competition or RCBS Gold Medal seater die
You can't go wrong with going to a good trigger like a Geissele Hi-Speed
Have fun with your new toy