How far can room treatments solve boomy bass?

I tend to side with Zman here. The usual sorts of room treatments likely won't amount to much more for you than a band-aid type of fix at best. If it were me and not knowing your budget limitations, I might consider, until you can get a better room anyway, the short-term fix of breaking down and getting yourself some sort of equalizer...yes, I said EQ! Possible insertion losses aside (which I think are often over exaggerated, myself), they offer enormous flexibility in just this kind of situation - expect your bass problems to be solved and then some. Perhaps a nice Rane unit on the used market, or possibly a digital EQ if you only have a digital source - a Behringer DEQ-2496 can be used in a digital passthru mode and costs peanuts...very little signal degredation this way if you are using it between a transport and a DAC for example. There may be other possible candidates out there, you just may have to do some looking, or ask others here. Hope this helps.

River251, for bass below 200hz try checking out the Cathedral Sound Panels. They are not absorption panels but instead work on the venturi principle which says that a gas moving through a small opening will speed up which in turn is related to pressure changes in the room from the woofers. To the drivers the room becomes effectively larger, acoustically. The frequency range of the panels is optimized by the size of the holes in the 11"x16"x2" panels that you install in the upper room corners. They control standing waves without rolling off the highs and are about 90 bucks each. I have not used them (I currently have the opposite problem you do, my 13.5'x15.5'x8' livingroom is largely open to the rest of the house), but I've heard others say that these panaels are the only type of passive room treatment that they use. Worth a look.

Sorry River251, just noticed your Q above about an actual HiFi-quality parametric. What I use is a Ric Schultz-modified Behringer DEQ-2496. Have a rather minimalist 2.0 system: Onkyo carousel changer as transport, out to a Monarchy DIP Combo, out to the DEQ being used as my DAC, from there to a pair of Endler Audio shunt attenuators that are plugged directly into the inputs of a pair of Monarchy monobocks. About $2k worth of Alan Maher Design's power-conditioning stuff rounds out the electronics. This is a single-sourced, CD-only system. The stock sound of DAC section of the DEQ is unacceptable for HiFi. However, many choose to use it between a transport and DAC - that way the DAC section of the DEQ itself is bypassed altogether and all the DEQ is responsible for is signal processing in the digital domain and this does improve the sound dramatically. About the only issue to deal with at this point is the cheap, stock switching power supply. It's unreliable as well as a bit noisy. Ric's mod gave it a quality linear supply. But, I took things a bit further and let Ric replace the stock analog output stage with one of his own design and opted for an updated DAC chip as well. This allowed its use as a HiFi-quality DAC with true, differentially balanced analog outs to the monoblocks. The cost for the DEQ and the mods was around a whopping $625. If you need an analog input as well, Ric can mod the existing input circuitry into something equally HiFi-worthy for a few hundred dollars more. But, for me the sound is glorious and the flexiblity is unparalelled and all that. The DEQ itself has 10 bands/ch variable from 10 octaves wide to 1/10th octave narrow at more than 330 individual center frequencies from 20-to-20k in 1/2db steps. All that with 64 user-defined memories. The processing is 32-bit. There is no volume out control on the DEQ (except for up to -15db at the DEQ's input to accomodate higher-gained sources). The DEQ has a steeper-than-analog learning curve to it, but you'll get passed that after a while...took me almost year to begin to feel really comfortable with it, but I was a bit impatient about it, as I recall. But, I dunno how to answer better your Q about what you might want without knowing your system architecture.

Ric can be contacted at his website EVS audio (Electronic Visionary Systems) and his location is in California. From there you can email or just phone him as I do. You'll find Ric very easy to talk to about anything. Just make sure with him (or me) that your Creek and the DEQ are compatible for whatever you have in mind...OBTW, your next step will likely reveal that Toslink, compared to SPDIF, is grossly inferior soundwise. Coax, if you can swing it (the DEQ can), will be a big step up!

Update: just looked up the Creek on their website - it does indeed have a coax digital out (or at least the original CD43 did, I'm assuming the MkII does too). Should be an excellent transport for anything like the DEQ, which itself will give you 96k upsampling which will, compared to your non-sampling CDP, will greatly smooth out the highs - decidedly less rough or ragged sounding, for sure...by extension, that will likely help a bit with imaging too.