to be honest, acoustic foams for listening/mastering room are usually ****, sorry;
1) thin acoustic foam kills highs, barely mids, so you are stuck with even more exaggerated bass freqs
2) acoustic foam in general has no chance to trap the bass (material not "heavy" enough)
3) pyramids/waves are good only for breaking and diffusing the waves, they don't effectively dampen anything, since the material is "cut" so there is literally no "fat" layer to catch the low freq waves
 
if you really wanna use acoustic foam, then you will need "fat" ones (I have built dead-dry recording studio using the "chocolates" and it does work much more usefully than just "pyramids") to effectively "catch" wider frequency range (especially mid-bass) but don't put them everywhere, and even then, you'll still need "heavy" and "thick" bass traps in corners,
 
if you want decent acoustic treatment, then rather consider mineral wool (rock wool or whatever is it called) - we use "Ecophon" in our radio studios, advantage of that specific product is that the wool panels have already applied "cloth" finish, so it can be used without any additional "layers" on walls, ceilings etc. in just wooden frames "as it is" (yes it costs probably more than good acoustic foam, but it's worth it),
 
from my own experience, I think it's really impossible to treat room right, especially when on tight budget, so maybe just get used to how your speakers+room sound and consider that when mixing/mastering (figuring out optimal listening levels does a lot),
acoustic foam panels look cool and definitely make "some" difference, but don't get overly crazy into exact measuring and placement....

Icing on the cake would be to invest in ARC 2 by IKMultimedia. Worth every penny.
Just my 2 cents.

ARC certainly has it's place, but only use it AFTER you've done your room treatment.

you can put the side absorbers for the mirror wall on stands (e.g. the round base mic stands) so if you need access to the closet it's easy enough to move. leaving the closet open slightly at the far end of the room will help with some LF absorption but the thin foam products are really only meant to treat reflections. you need deep foam or GIK products (or real traps etc) to cover the corners. if the room is 8x10 (w/ 8' ceiling) you'll find that the room response is pretty uneven in the LF range because the even and duplicate values of the room will reinforce (and conversely null) a number of frequencies (primary and their respective harmonics). so deep treatments will be better over all.

Thanks everyone for all your advice! Really helps a lot. I realize I'm not going to have the perfect set-up, but I figure something is better than nothing. We'll see how it goes.
 
Thanks again.
 
~Jeff

There is merit to the "long" approach mentioned above. I have hardened surfaces in my room, so fire the amp off and record vocally diagonally to maximize scatter on reflections. Volume is another consideration, since less power = less reflection. There is no requirement to mix at a level that will degrade hearing over time.

I think it boils down more to doing the best with your environment and adapting accordingly.

KingsMix
Icing on the cake would be to invest in ARC 2 by IKMultimedia. Worth every penny.
Just my 2 cents.

ARC 2 is definitely a great help after you have set up your physical room treatments.  And only after you have done what you can with traps and foams, monitor placement, etc.

I think the first thing to do is to go get a hearing test.  I've been to concerts where some idiot had his head inches away from the HF driver of the mains.  Is that you?  I'll type louder.  What always killed me in major studios with all the room treatment, room shape etc. is when they'd switch over to the Auratones to "check the mix".  You also have to take into consideration that most music is now listened via lossy mp3s played thru earbuds.  Grain of salt here. 
 
 

depending on how finicky you are, rockwool (or mineral wool) is cheap and you don't actually have to do too much to it for bass absorption.  In the US, 12 4-inch thick batts are about $50 at Home Depot/Lowes (you can order and pick up), which is more than enough to help your room.  I cut and stuffed 8 or so batts into pillow cases and then burlap coffee bags and leaned them up against some open corners while waiting to hang them.  That cleaned up the lower registries nicely.  Even worked once up on the walls (including corners).
 
Now when music fades, it disappears rather than sinking into a soup of low-frequency noise.  You'll understand when you hear it. And diminished slap back once they are hung. Sweet.