Why are big speakers in small rooms bad?

Thats "would" be in order =)

I'm in similar situation. My room is 13x17x10.3, which, from reading around, is a small(ish) room (about 2200cf). I am currently using Studio 100 V1s that are probably too much for the room. The room is treated with Echo Busters products and some wall "hangings" and the 100s sound very good but I still have some significant bass "humps" that I've measured. It may or may not be the 100's fault, I'll know better when I get the Silverline Sonatinas I ordered. The best I've heard the 100's is currently 65" from back wall and 42" from the side walls. I sit about 7-8ft from the speakers leaving about 3-4 feet behind me. Closer to the front wall, the 100s were boomier and the soundstage shrunk.

Like others said, you need to listen for yourself and you will need room treatments (any room should have them if possible). You may want to get a SPL meter and some test tone discs. Part of my problem is the room is on the second floor and the floor is wood (rug covering). I'm thinking of trying some type stand to help isolate the speaker vibrations from the actual floor if my new speakers have the same size measured bass humps.

The speakers may or may not work in the room... you can only try it and see.

I have "big" speakers and they work ok in my room; although not perfectly.

A trick you might do is to try arranging the speakers diagonally.

This will gain you a little more room from the speaker plane (this worked wonders in my application - better soundstaging and improved bass).

Still need bass traps though... Of course YMMV.

Good Luck & Happy Listening!

standing waves...

Here in lies the problems with big full range speakers like the gold's in that room...First, placing the speakers where they yield the best response in the upper bass, will not be the case for the deepest base. Thus, often, you'll either be dealing with boomy unatural lower bass, or compromise the accuracy further up. Soundstage width must be balanced, and the seats (as the speakers), are going to need be out in the room, probably further than you'd like often. With seats placed properly out at about 1/3 of the rooms's length, you'll have to put the speakers out away from the sidewalls, and closer together, or you'll be boomy bellow 63hz reigion. So, soundstage width will be restricted full range.
If you do place the speakers on the long wall, you can help things often. but you should still consider 1/3 seating locations. Speakers would start at 1/6th from the front wall. If you have a solo-seat setup, speakers should be considered at 1/4 from sidewalls, if you sit in the middle of the room, yet staying 1/3 from front to back. These are good guidlines. But you still need to find where the speakers get best response overall. If you run the speakers as small, it helps your flexibilty, if you go "subwoofer".
Basically, if you run them full range for music, and don't cross over, the above mentioned will be your challenges, among others.
A possibly better option, if you chose to run the strong, dynamic, and deep sounding "Gold's" full range, is to "biamp" them! You can then get a good Parametric EQ on the bass woofers, without affecting the mid/high's! Otherwise, consider a good investment in the Rives Audio "PARC"...the best analog Parametric EQ ever made IMO.
Basiclally, your main challenge in a small room, is yes, the Bass response and setup. You'll have only a couple of options, as is. With EQ'ing you have more.
I could make the Gold's work in that small room, but it wouldn't be easy....