Ok in responses to your questions/statements "Drrdiamond", if you have a 15 X 25 room, and you are using a corner placment, it's acoustically impossible for both your speakers to be in the same SYMETRICAL acoustical space in that room!!!...can't happen! (infact give me the speaker placment spot measurements in relation to each wall and I'll tell you what your frequency response is going to be precisely with those speakers!!!...but draw me a room picture first, so I can factor any oppenings, doorway's and windows and such)
Because your room isn't a perfect square(i.e, 25X25, etc..which would have different problems acoustically). infact, you will probably be putting your speakers much closer to the respective walls in this corner scenario, correct! That's defitely going to give you boomier and more peaky sounding bass response, as the closer you get to any wall/boundary with either your chair or speaker, the more uneven and unatural the bass response is going to be!...and that afects the overall spectal tilt you hear, and potential overshadows the midrange and treble.
Again if you want to test this, just place some saller, even inexpensive modest sized yet smaller, monitor speakers on stands where you're considering placing your seakers in a "corner" placement, and measure!!! The response from both speakers in the bass reigion will be VERY DIFFERENT! Then try putting the same speakers in a symetrical long wall or short wall set-up(considering other openings), and you'll see EQUAL MEASUREMENTS AND BALANCE FROM EACH SPEAKER!! (In fact you can call Thiel, Dunlavy, Wilson, Logan, B&W or others and they'll tell you a lot of the same!)
Also, YOU WILL DEFINITELY BE HEARING REFLECTIONS FROM THE SOUND FROM THE WALL SPOTS TO THE IMMEDIATE LEFT AND RIGHT WALL BESIDE/BEHIND YOUR SPEAKERS IN A CORNER PLACMENT SCENARIO, MUCH EARLIER THAN YOU WOULD IF YOU KEEPT THE "LONG WALL" SET-UP YOU STARTED WITH!(that is unless you had your speakers ultra wide or close to the front wall with your "long wall set-up"! With a corner placement you are forced inTo placing the speakers near the walls dirrectly behind/beside the speakers. And its those locations where your going to have to treat and deal with first order reflectons! ...mostly much earlier and "simultaneously"(which is a problem) than if you followed the "Dunlavy" recommended symetrical speaker placment arrangement along a long wall(or even short wall) symetry!
I've been around this stuff for 20 years, and have set-up more systems than 99.999999999% of all living beings on the planet, so I've delt with it all time and time and time again, and nothing ever changes! So my recommendation would be to call any high end speaker manufacturer, and tell em your quandry! Tell em you would like to consider their speakers, and want to know about placement chioces and results! You'll get a huge majority of them recommending the "long wall" or "shot wall" SYMETRICAL ARRANEMENT, but a staggeringly very few recomendng "corner placement! Is a corner placement workable?..perhaps, but not likely with such large speakers in a relatively small acoustic space as yours!...and,yes, 25 X 15 is still a relativey small enough acoustical space. At any rate, it couldn't hurt to try your corner theory ultimatey(that is unless a 250 lb speaker tips over on ya that is...he he.). But when you do, try measuring both speakers like I mentioned, YOU WON'T GET EVEN CLOSE SIMILAR RESULTS FROM 20HZ-300HZ!!!!! One speaker will measure decidedly high in one frequency, and the other will measure either flat or low in a lot of frequencies. Try it, you'll see/hear! Bass will tend to seem stonger, or at lest different from one speaker than the other, which makes an accurate pressentation impossible ultimately
Actually, if what your saying is the dimmensios are a perfectly closed in rectangular 25 X 15, and you tell me where your placing the speakers in exact distances from each speaker to each wall, I can tell you what your measurements are going to be!!!!!!!....to within very accurate measurements!!!!...and trust me, you'll not get the same balanced response from speaker to speaker in that corner location, believe me. Or simply try it and you'll find out really.
Anyway, if you could see your room from an acoustical "bass wave" standpoint, you'd understand why I say what I say. From right to left, from front to back, from ceiling to floor, you have very different bass response in all different spots in that(or any) room! If I could draw you a picture I would
Anyway, good luck with it.