well, what about the EQ on your amp? you should be able to get a warm sound by using the neck pickup, rolling the treble off, plenty of bass and mids, as well as setting the tone control to around half on your guitar.
String action can also play a part, the higher the action, the fuller and stronger the sound, also where you actually pick the strings makes a difference, play a few bars strumming over the bottom of the neck and you'll see what I mean. I respect you not wanting to use effects, but dont let that attitude restrict you, in the future you might come up with a piece that would sound excellent with a touch of flange, or wah wah.
Just throwing my 2 cents worth in. I would have thought that your guitar would have a huge sound anyway. DiMarzio make good pickups, and also PRS dragon pickups are fantastic, I have them on my PRS singlecut and it's the best tone I've ever heard, really sweet and full on the neck