Hi jwusoccer,
For a second opinion I probably couldn't disagree with much more with QBoQBoc's assessment. Let's start with the disclosure that I own the V6-Stage in universal form, and because they regularly blow me away, I'm likely a bit (or more) biased towards them. On the other hand, I'very been fortunate to listen to a lot of really good phones this summer to compare them against. This includes 1964Ears Qi, V6 and V8 at the summer Seattle meet; the entire Noble line-up (including the K10) for 4 days, the Beyerdynamic T90 & T1 for at least a month, and the new HE-560 which I currently also own.
First let me correct the misconception of the V6-Stage having less bass impact than the V6. The opposite is true, and this is clearly shown on the 1964Ears website. The V6-Stage flat out nails sub-bass, bass, and mid-bass! Overall the the $1600 Noble K10 outperformed the V6-Stage, but not in sub-bass extension and bass details.
To my ears the Qi and V6-Stage are 1964's best products for the money. If you're budget hits the ceiling at $550 then get the Qi and don't look back, just enjoy them. If you can swing the extra for the V6-Stage then go for it - you won't be sorry. Better bass extension & detail, no mid-bass hump/blead, mids slightly more forward with more detail, and more high-end extension and considerably more high- end detail.
In addition to to frequency response is realism. Soundstage, instrument placement, coherence, etc. all done well and in unison, is another way the V6-Stage (and the V8) really shine. The Qi and V6 don't have key1964 technology in Triple Bore Design and 3D Soundstage.
All IMHO and per my ears!