Are you making the panels yourself or buying ones already made ?
If you were to get ones from this site:http://www.gikacoustics.com/gik_242.html
then its just a matter of figuring how many you think you need and then doing some simple math( this site does the total for you ).
What makes you think you need to treat your room?
What does it cost? Well, doesn't that depend on what your room needs? If you can't define what problem you are trying to cure you are getting ahead of yourself to assume your room will just sound better by using commercially available treaatments. If you are not careful you could just end up spending a lot of money for the wrong stuff and end up with a room that sounds worse than it does now. And, to make matters even more interesting a lot of potential or real problems can be resolved by domestic furnishings strategically placed and or speaker set up.
Think it out................
$700-900, assuming you buy used. As newbee remarked, the challenge is to find out what the problem is. Lastly, every room needs to be treated as perfect rooms only exist for perfect people, all can be improved.
Above 100 Hz not all that difficult or pricy but for smaller rooms is worthwhile. In an earlier small(er) room setup I used 4 Corner Traps and 4 Tune traps together (cost was around 350-400) rather successfully (some of them now not needed and are for sale!). Experiment and Experiment!
GIK is great for the money. Real traps start getting pricey but they are well built, their web site is worth a visit just for the info on room treatment they provide.
Just start with the mirror points on each side wall between you and the speakers. Second is treatment behind the speakers.
One thing to think about is that you can't EQ bass room nulls, and using an eq to reduce peaks does not sound the same as reducing them with room treatments...a treated room will have faster time response.
So you may want to consider doing a low frequency treatment in corners behind the speakers in addition to the EQ.
One way could be to buy and read a couple of books (ej, Everest's and Floyd's books) to understand what's going on, get an SPL meter from Radio Shack ($60?) and a CD with test tones and start experimenting with home furnishings, comforters, etc to further understand what might work in your room. Then you could either buy or DIY treatments (receipes available at AAsylum, for instance).
I'm going down this path and while it's been a lot of work it is being fun and I'm learning a lot as I go. It's likely the cheapest albeit most time-consuming approach.
My two cents. enjoy!
Also another question I have is, if I treat the room, then change my amp/pre, would I have to make any adjustments with the room treatment? All audiophile amps/pres are supposed to give a flat response, correct? So my guess is I would not need to change anything with the room treatment or remeasure unless I change the speakers. Is this true?
Yes it is true. BTW Room treatments do not really change frequency response of audio equipment so much as room treatments will reduce or remove the audible effects of reflections off the walls. That can make it sound better or not depending what the reflections add to the sound that you find objectionable or pleasurable..
If you treat your room properly you should be able to tune around system changes by adjusting speaker placement and toe in. If that doesn't do it then removing or adding treatment can be done.
After treating your room you are most likely going to want to play with speaker placement anyway as most likely you are compensating for the sound of the room with your current placement and toe in.
You can fake room treatment with a few pillows just to see if you want to put the effort in. I myself wasted a bunch of money in years past on 'warm' cables when what I really needed was treatment behind my speakers and at the mirror points and a touch less toe in. Ended up getting rid of the brightness and huge improvements in detail, soundstaging, and pace.
I would read up a bit before you do anything.
The Room treatment vendors sites that have been recommended have a lot of info. I also like Jim Smith's book "Get Better Sound".
I plan on getting the help of a professional acoustic engineer to help with my room treatment. Right now I have a pretty live room, with definite flutter echo. What can I expect post-treatment? Since the room will be "less live" than before, am I going to have to use more amplifier power to reach the same volume level? (I like to listen pretty loud, usually 85db) If yes, how much more amp power are we talking here? I'm using B&W 805S in a 15x17 room right now, and they fill the room with sound quite well. I am hoping they still can fill the room nicely after the treatment.
Best of luck! I need to learn more about room acoustics very soon...let us know of your progress :-)