Change the cartridge or phono stage

Elevick is correct; you want no coloration out of the table/arm/cartridge at all. Start with a good protractor, scale and a powerful magnifying glass. Adjust the VTA so the scale is at record surface height when you've dialed in the tracking weight you want to use. Next, get the stylus centered in the target and get the cantilever precisely aligned. Constantly re-check this part and take your time to get it just so. It will be worth it. After that's all done, listen to some material you know really well and decide if you think it is brash, muddy or blooms. Those are symptoms of incorrect VTA and damping/level/warp, respectively. After all those points are identified, you can then give thought to changing things. Note that the cartridge can have a big effect and should be a strong compliment to the speakers. Warmth is something that is usually best obtained with a tube component somewhere. There are a lot of different opinions on the best way to go with that end of things, so do your research first. Have fun & good luck!