People will say - If you wish to run a professional studio, you should behave like a professional studio. But the fact is no room is perfect, and what listener listens in an acoustically treated room? A lot of engineers I know make sure that they identify what is wrong with the room / speaker placement and learn what it does to their mixes. I would imagine using eq pre speaker would not be a good idea, I realise I'm not fully answering your question. You certainly don't need loads of expensive acoustic tiles, and angeled ceilings and no paralell walls. The simple placement of furniture in the right place, speaker position and creative interior design can do wonders, and makes your studio more interesting than all the other, dark grey clinical rooms - unless you want that look. There is a great chapter in Mike Stavrou's book MIXING with Your Mind, that deals with listening to your room and building your studio to work with your space.
I will always try to find a solution from what I have rather than go out and buy loads of shit that sound on sound or audio media says YOU NEED! Unless of course you are pulling in international artists - they kind of like the xpensive treatments and fancy lights and whistles to justify the £1k a day they pay for studio space!
Try to make your room work and learn whats going on with your speakers before you reach for the cheque book - hell you just brought a three story town house, you've spent enough money already!.
All that being said and I know I've said alot - does anybody have a definitive psychoacoustic reason as to why we shouldn't use eq to correct room problems. My opinion is that you are correcting how your mix sounds in the room and not the room itself - the mix wont therefore translate well to another room.?