For a boomy room, what panels will reduce mid-bass

Before getting panel or ASC tube traps, move your speakers away from the front wall and side wall. Toe in the speakers. It should help.

You might try some new and less boomy speakers.

I 2nd the tube traps, very effective and well worth the money!!

As mentioned earlier, placement of your speakers has a lot to do with it. Try putting the speakers 1/4 of the way into the room for each wall (for example, if your room is 10 by 12, put them at 2.5 by 3 away from the wall). If this dramatically reduces boominess, then you will know what to do.

Try GIK Monster Bass Traps. They are not expensive and VERY effective. I agree that sometimes a room is just too boomy on its own. Moving speakers and listening chair can locate a specific spot where the standing waves cancel just right, but that only helps if you sit EXACTLY in the sweet spot. Talking and walking in the room still reminds you that it is the acoustics of the room that need to be improved. ASC Tube Traps have been considered the best for many years. They are expensive, and the ones for bass are large diameter, tall and require floor space. Recently I discovered (and now prefer) "Monster Bass Traps" made by GIK Acoustics. These (and the less expensive Model 244) were designed for studios, they hang on the wall, and they truly absorb the reflections between 80 and 500 Hz better than anything else have experienced.