I am new to home theatre, but have decided to go ahead and start to build a system. Let me start and say my room size is roughly 15X15 with 8 foot ceiling...
Hmmm, Square room... You're going to need some acoustic treatmenst for the room but that'll come after buying your equipment. Is this strictly HT or is for music as well?
As for speakers I am one that really has not sampled different brands yet, however I was in best buy the other day and liked the definitive technologies and the way the sound they were around 600 per speaker. I plan to go with in wall speakers if I can instead of floor standing if I can fit it into my budget. Does anyone know if floor standing speakers will cost less then wall mounted? Also which ones should I get better quality out of? I'd also like to get a 5.1 system, but if I can afford it, I would consider 7.1. Also I know some speakers come with a built in sub, so I would consider them as well so I won’t have to spend extra on subs..
So, you liked the def techs? Thats a start. What I would do is to take a pad of paper with you, write down the make and model of each speaker you audition and what you liked and disliked about the speakers you were auditioning. What about the sound did the def techs appeal to you? Was the bass tight and deep or was it boomy and loose sounding? Were the mids life like or were they hollow or just too pronounced? Was the treble irritating and harsh or were they dark and not revealing or were they smooth that made you want to listen for more? How was the imaging?
Bring music with you that you are very familiar with and know quite well. To make it easier to audition HT speaker systems, listen to the main speakers in 2 channel mode with music. Music is much harder to reproduce acurately then a movie soundtrack so if the speakers do well with music, then they will do well with HT. Speakers that do HT well may not do well with music. When auditioning the center channel of the same brand and series as the main speakers, , pick a difficult source like an announcer that mumbles alot. If you can makeout what the mumbling announcer has to say, then you have a good center channel.
How about Axiom speakers? Has anyone heard these in the store? I know they offer a try and buy which can't be beat. However you need to pay shipping back to them if you are not happy within 30 days. Personally I’d rather sample these in the store before I make an investment in them..
I would go to speciality stores first and start auditioning speakers first instead of going to the internet first. Once your likes are determined, you can mention them here and fellow members can make internet brand recommnedations based on your likes/dislikes. The specality stores are better setup acousticaly then the big box stores which will make auditioning a little easier. It will give you an idea of what you like in a speaker.
Keep track of what amp or receiver is powering the speakers you're auditioning. Try to get a receiver/amp that closest resembles what you have or want to get. It just reduces another variable when audtioning speakers.
My problem is I don't have a great trained ear on what to listen for. I want to know what to listen for to hear the difference between a Bose system and a Dev Tech system, etc. Where will I hear most of the crappy quality on the low end speakers? Will it be when the volume is low? Will it be when playing music or blasting it? I really need advice on this. .
One thing to keep note off. When auditioning speakers, make sure the volume levels are matched between the diiferent speaker pairs because the louder speaker pair will always sound better. Listen to levels that you think you would listen to most of the time because thats how you are going to be using them most of the time. Blasting is fun too

but only do it if you think you'll listen to them at loud volume levels once in a while. Refer to my 2nd paragraph for a few points to listen too.
Is it possible to do this on my budget? Can I do it for less? Or will I need to spend more. Any advice appreciated.
Only auditioning many speaker brands at variois price points will determine that for you.
I hope this helps.

Let us know how you make out.