Actually, create your emblem @ 2048x2048 ( A little big but okay).  Have your other texture file open, click on your emblem and drag it to the texture window.  Another layer will be created with your emblem over the texture and of course the emblem will look enormous.  Now, I believe, go to edit >transform> scale ( Bear with me, I am not on my home computer).  Hold the shift key down and the scale the emblem down to size.  The Shift key will retain the proportion of the emblem without distorting it.  Move the emblem into place then merge the layers. 

What you were describing in your post was actually changing the image size by resolution.  There is a difference.  What you would like to do is retain a hi-res to your emblem when moving the layer to the texture.  I do have a test image of a render but having a little problem uploading to photobucket.  Once I resolve it I will post it.