Depth of sound stage--I need help

I own the 333es which is a good enough unit but really does lack the resolution to presnt the ambient cues to give you a 3D soundstage. When compared with a bel canto dac I had it most notably lacked depth. I have since sold my bel canto and had Dan Wright of ModWright modify 333es for $350. It was an amazing transformation and on redbook beats the bel canto or PT combo and is unbelievable on sacd. I can recommend this as the most cost effective solution to your problem. You are suffering forom a lack of resolution, the AP speakers can throw an amazing soundstage( I have the Virgos) and the quicksilver tube gear should be great.
check out www.modwright.com

I have found that MIT cables create a very deep and wide soundstage with great imaging.

I agree with Chelillingworth, your 333es can definately be improved. I have repeatedly stated for some time now about how Sony (and virtually all other Japanese cd players) use very meager sounding output devices. We are talking about cheap op amps here! THERE IS NO EXCUSE FOR THIS KIND OF OVERSIGHT IN A HIGH END AUDIO APPLICATION! Everyone that has a Japanese player should have this oversight fixed first, BEFORE they spend needless thousands of dollars on those high priced cables and isolation systems. Shouldn't we correct those big design oversights first which seriously limit the overall sonic performance, and then tweak our systems? How can you extract great sound with those expensive tweaky items if there is a serious sonic limitation at the source? Another modder to consider other than Dan Wright is Stan Warren. Both have received high acclaim at Audiogon forums.

Your intuition is correct - there is no substitute for properly executed SE's in an appropriate system in terms of spatiality. What people tend to forget, however, is that space is not perceived simply in terms of proportion (width and depth), but in terms of its nature. What does this mean? Space is not separate from the soundwaves that move through it and a stereo should lend the perception of this nature. With SE triodes - properly matched to a system and invariably NOS-tubed - the movement of the sound through the space is more "real" to our perceptions (that perceive such existential cues at a very deep level of listening). What you desire, but find it hard to articulate because you have perceived these spatial qualities at a deep level when you weren't thinking, is not only volume created by the parameters of width and depth, but also a spatial correctness. If you want this now, then you must consider moving beyond EL34/6550 push-pulls. Incidentally, get the Modwright mod; not because of depth considerations, but because it will improve imaging.