I think the best modifications I made to my 700 was adding a Timney Trigger and adding a Tactical bolt handle.
I could not get the supposably adjustable X-Mark trigger to adjust lower than 5 lbs (perhaps mine was a lemon) and I am not handy enough (or foolish enough) to modify a factory trigger. The Timney was a simple drop in that required only a few punches and some patience.
I mailed my factory bolt to Badger Ordinance who added a tactical bolt handle to my bolt and shipped it back to me.
Yes, the Badger tactical bolt looks cool, and I no longer have sores and cuts on my fingers from banging them against the scope while cycling the action rapidly.