Great sound possible using a Subwoofer?

My speakers are flat to 38 hz but I feel I'm still missing impact, power and weight on most of the pop/rock CDs I listen to. I don't know if a high quality subwoofer would be a positive addition to my system or just add unrealistic bass and muddy up my midbass and midrange. If anyone has extensive experience with this dilemma please tell me what you think. (would better isolation of components, cables or power conditioner help the low end?)
Nick read"what tube amps loosen up in the bass?"
Nick, play a test VCD with third octave pink noise, listen in the listening seat, and see if your pseakers really are flat to 38 Hz in your room. They might not be.
That's CD of course, sorry for the typo.
If your speakers are flat to 38hz, you should have absolutely no problem with bottom end weight of your program material. There are really very few instruments which reach that low, anyway. Two are the piano and the pipe organ. If your system goes that low, it should be rattling the floor. Also, rock music, while often filled with a lot of bass, is usually not very deep. Most rock music is rolled off well before 40hz. A good CD for testing the bass capabilities of a system is Sarah McLachlan's "Surfacing". If track 2 does not shake the floor, your speaker manufacturer is lying to you, or you have some bass extension problems upstream in your system.
In many ways a speaker that goes down smoothly to 40Hz is an ideal candidate for a subwoofer. It's much easier to crossover from the sub to main speaker if the main has reasonably deep bass response. It allows the sub to just work the deep bass without having to work up into the mid-bass region. However, most popular music doesn't have alot of content below 40Hz. A typical pop mix hypes the 80Hz region in lieu of deep bass, so you shouldn't expect to hear a subwoofer on all music. In fact, if the sub is correctly setup, you shouldn't hear it all that often. But when it hits -- you should feel it. None of the other changes you're considering will do what a good, well setup subwoofer can.
I think the real issue here is what type of amplifier are you using? Accurate reproduction of low frequencies requires a lot of power. This is why most powered subs will have dediacted amplification of 200 watts or more (preferably). Adding a well-made subwoofer to your system will free up your main amp and allow your speakers to open up. HOWEVER, for the same expense of a good subwoofer you may want to consider a heftier amplifier. It sounds like some experimentation is in order. I went with a subwoofer to get that extra low-end punch but a lot of my decision was based on the fact that I wanted to have a HT set-up also.
Here's my $.02 on this. I'm running Aerial 7B's on the front channels of my home theater, and do a lot of 2 channel CD listening. For the better part of a year, I was using an older, inexpensive subwoofer, for LFE only, and all two channel stuff was run through the Aerials with the sub turned off. The Aerials have been measured to flat to 30Hz by Stereophile, which is lower than they're rated. I recently had the opportunity to buy a demo Aerial SW 12 subwoofer at a good price, which matches the rest of the system. I have A/B/C tested the following combinations (through a Lexicon DC-1, which admittedly is not the best two channel pre-amp), with all subwoofer crossovers being made in the digital domain by the Lexicon: (A) 7B's run full range, (B) 7B's crossed over to the SW-12 at 40Hz, with the sub low pass filter set at various points between 30 and 40 Hz, and (C)the 7Bs crossed over to the SW-12 at 80HZ, with the low pass filter on the SW-12 at various points between 50 and &0 Hz. The SW-12 was adjusted per the manual. First, although the Aerials sound great by themselves, the bass sounds much more detailed and solid using the SW-12. I actually hadn't planned on using it for anything but home theater viewing when I bought it, but it is now used for all two channel listening as well. The best results were obtained with the 80Hz crossover to the 7B's, and judicious use of bass gain control, with the low pass filter set at about 57Hz. The bass in the 7B's melt into the sub in a way that makes it impossible to know if the sub is on when sitting in the listening position. The bass is tight and deep, with none of the muddiness I experienced with the old sub. Also, by in effect bi-amping the system with the sub amp and the Aragon Palladiums which run the L/R channels, I have no concerns that I'm muddying the mid-bass, mids or highs because of power soaking by the bass. I also note that on tracks where the bass is coming from the left speaker, even though the sub is on the right side, the effect is still to anchor the bass on the left speaker, no matter how deep it goes. I believe the higher harmonics still come through the 7Bs and localize the entire bass range to that speaker. It's pretty amazing when you first hear it. So, in answer to your question, I was really happy with my main speakers before the sub, but it's now clear to me that, with a high quality sub, and experimentation with the crossovers, you can have much more control over the bass and greatly improve the overall sound. Jeff
My experience is similar to Jeff's. I find the better the main speaker is at plumbing the under world , the better, easier and faster it is to integrate a sub. My Apogee Slant 8s go down to a solid 25 HZ in my room and I was quite satisfied. Then I auditioned a used Velodyne FSR-12 that a dealer had for a very good price. Using the internal x-over from the Velodyne for both the high pass and low pass functions, I dialed the critter in in only about 30 minutes of tweaking. What a difference! With the bottom end of the Apogees rolled off below 80 HZ, they could play insanely loud. Got rid of a nasty mid bass peak in the room, and had a more transparent, larger and better defined soundstage too. The bottom end was deeper (actually got that last 5 HZ), tight as a nut and positively thrilling on some stuff. Definately worth the $700 I paid for the sub and it definately complimented the main speaker.
subs *will* help your set-up. note, i said *subs*. getting only one will degrade your sound, you gotta get two. it is definitely easier to cross subs over to speakers that already have decent low-end. a steep-sloped active x-over is also helpful. look to vmps for the best subs for the $$$. you can get a pair of their top model subs, along w/active x-over & amp(s) for less $$$ tha *one* top-line sub from muse, velodyne, rel, etc.
Subs will add but you must have two or the sound will not time align properly. You would be best having the subs placed closer to the rear wall than the other drivers as well. Most drivers get highly directional or beamy near the end of their frequency ranges so by having a sub you can crossover the main speakers about 1-2 octaves higher and open up the sound stage, and of course the sub will not be beamy- provided that the drivers are not too large relative to the drivers on teh main speakers. Ie a 4 inch main speaker midbass driver will not cross over well to a 15 inch or 18inch sub. MOre like a 4 inch driver crosses over well to a pair or 6.5 inch drivers or perhaps and 8. A pair of 6.5 inch main drivers cross over well to 8 inch subs, or a 10... get the picture? Good luck.