speakers or room???

I have a nagging problem with a frequency spike in the midrange that I especially notice in acoustic piano (jazz and classical) and sometimes vocals. I have heard this in different speakers including SF Venere 1.5, Dynaudio Emit 20, Martin Logan motion 15, Zu Dirty weekend, and various other 2-way designs. I have not had this problem with Polk Lsi m703 3-ways, and some 2-way DIY towers that I built a few years back. Back in the day when I was still using an MXR graphic eq, I would roll off  the 250 - 500-1000Hz sliders 3-6-3 db for a more balanced sound. I stopped using it because it introduced it's own coloration to the sound.

My listening room is a small family room adjoining the kitchen for a fairly open space about 15 X 30 with a cathedral ceiling in the family room portion. The flooring is oak hardwood with 8 throw rugs in various places. I would describe it as being fairly lively, although the kitchen island, cathedral ceiling and a fireplace create some asymmetrical surfaces.

So me thinks it could be:

a. speakers, especially 2-way
b. the room, too lively, not well treated
c. my hearing going wonky at age 67
d. all of the above

Any and all thoughts, experiences would be most welcome.

Current system:
Hegel H80 or Primaluna Prologue depending on the mood
Tannoy XT8 speakers

Actually OC fiberglass isnt very effective when compared with an engineered cotton or wool material designed for this purpose. I bought some cotton material from a company called Soundproof Cow which I think is very good. If you want to go cheap then the OC is fine but it doesnt absorb a very wide band of frequencies.
The Tannoys look like lovely speakers, and published measurements don’t show a peak there. But the two octave around 500 Hz are an area sensitive to speaker positioning, especially with ported speakers. So my suggestion is, try moving the speakers away from the wall a little and also moving your listening position. You might be able to fix this that way.

As far as room treatment, that’s something I often recommend, but these frequencies are low enough so that a thin panel or rug isn’t going to do anything to help. I would use panels 6" thick or something like tube traps. Still, I’d experiment with positioning first. You might not need room treatment for this particular issue.

Finally, I have not used one, but many users swear by the Schiit Loki, saying it's a useful and transparent EQ for very little money. One of its bands is centered at 400 Hz, which might be just the ticket if you can't solve the issue with repositioning the speakers.

dtapo... don’t want to ruin your day but at 63 i’ve just realized that my hearing has changed. in the last few months all of my mid fi gear and car systems now have their treble controls at max boost. never needed that before. max treble boost was way too bright maybe as little as a year ago. ain’t happy about it. fwiw
I have the XT8 speakers as well, also fed by some Primaluna gear. I listen to a lot of jazz piano (as I type this actually) and have not had any issues with any midrange spike. I actually used a mic and REW software to do some room measurements and did not see any spike there. So I’m also guessing the room might be in question here. 
Your source might be able to help with EQ. I use Audirvana (on a Mac feeding my DAC) which allows to use some EQ plugins that I set to compensate for the REW measurements. It probably won’t do as well as some of the recommended room treatments, but it’s an easy test to see if you can “adjust” it out. 
First things first...probably get your ears tested by an audiologist.  That's not realistic at this time...so at least do a few sweep tests on youtube.

Then examine the room...then speaker position...then different speakers etc..

I have tinnitus (4000hz notch) from an ear infection at age 25.  Earlier this year (at age 52) I got a bass boost (way too much) in my left ear and then suddenly lost nearly all the bass and mid tones in my left ear. When you loose mid and low bass you can't properly locate who's talking in a room full of people. It sucks...especially when you've just plunked some good money on your first tube amplifier.

Anyway, I like you, had a boost in the mids that were annoying when listening to piano or when vocals hit the right notes.  I think when you loose some frequency spectrum, your brain compensates by turning up
the other frequencies.

I went to an audiologist and was treated with steroid injections in the eardrum and prednisone...lots of follow ups and nothing. I was told that the condition was most likely permanent and that a hearing aid would be necessary. 

The good news is that unlike upper frequency hearing loss, low tone loss can, sometimes, be recovered by itself or through therapy.  In my case it came back by itself only very recently but not to the same level as before...but I got 70% back. When you get it back, your speakers magically regain that lost imaging...a drive in the car sounds completely different...and you're not asking your wife to repeat everything she says. 

I've always worn earplugs to concerts and movies since my first episode of hearing loss at age 25. I've been so careful with my hearing but it's age and trauma that does our ears in. 

Good luck and happy listening all!