severe limiting factor

Well, if you could tell us more your room's dimensions and placement, as well as what you mean by "no soundstage or imaging". What are your expectations and what do you get. Could be the result of many things but your speakers, amp and preamp are certainly up to the task of giving you a reasonably good sense of imaging and soundstage. And while the Magnavox may sound shrill, dull, whatever, and can easily be bettered, it should not present as you described.

I agree with Tunes4me that your speakers could well be wired out of phase. A good check for this is to play a mono source, like a voice. If you are properly set up you should have a very sharp center image. Additionally, assuming that solves your first problem, don't be afraid to move your speakers closer to the sidewalls and cross the axis of the speaker well in front of you. You can get a much wider soundstage this way and you won't have an overbright upper midrange/high end from listening on axis. The severe toe in will help avoid the early reflection problem from the side wall. The only downside is you might elevate your bass.

Jsawhitlock - Your advices, while good, don't really address problems created by Thiels - They are not made for listening that far into the nearfield as you have suggested. Thiel recommends a listening position further back so the drivers in each speaker will integrate. The bottom line is that the posters room is basically too small for proper set up of the Thiels in the first place.

Sean, The problem which I was addressing was that a poster Jsawhitlock, in his first post, made a recommendation that the listening position be at about 7 ft with the speakers placed 6 ft apart. I have no argument with that recommendation except that its contra to Thiels recommendations and my personal experience. Thiel recommends a greater listening distance than 7 ft. As you say, 9 ft would be fine, except that when listening to the speakers 6ft apart from 9 ft away you lose (compress) your soundstage substantially - ergo, my (and your) original recommendations that the speakers be placed closer to the walls and toed in substantially to avoid 1st reflections from the wall. The problem with toe in on Thiels is that on axis they are IMHO unbearably bright, thats why when I recommended toe in with the axis well in front of the listener I was trying to set them up to minimize early reflections and on axis brightness. In a good set up for Thiels with a listening distance of 9ft the speakers would be about 8 1/2 to 9 ft apart, pointed straight ahead, and be several feet (3-4 would be best) from any wall, and even then the wall should be treated. Obviously they should be 3 to 5 feet from the back wall as well. Interestingly, while I believe he will have to compromise his listening experience substantially with the Thiels in this room, this room could work quite well with panel speakers firing down the length of the room as these can be placed quite close to the wall without creating large 1st reflection problems. By the way, are you aware if this fellow ever solved his apparent phasing problem?