Which brings us back to the original question. Surely all basses are acoustically warm so I'm assuming that unobasso wants to warm up his amplified sound ( he may not have 'a good amp' whatever that is). A quick fix in such a situation is to take all or some of the middle out on the preamp. Or fit a buffering preamp in line, such as a Fishman Pro Platinum.
smart answer, but the basis for your assumption -- "surely all basses are acoustically warm" -- is circular. the OP asked how to get more "warmth". if all basses are acoustically warm, then how can you get more of that? play two basses at once? fact is, some basses imo have less of that "warm sound" that others.... and if that is so with unobasso's bass, i.e., it lacks "warmth", then i just don't see how he will get more warmth through EQ. somebody please correct me if i am way off there, maybe it's just what you mean by "warmth"...