BPT 3.5 Signature vs. 3.5 Sig PLUS

I'm interested to know if anyone has owned and heard BOTH these BPT 3.5 conditioners, and can shed some light on what the PLUS does differently than the 3.5 Signature version.
The PLUS is more extended and neutral as well as more dynamic, it's not as dark and colored.
Thanks, Owl. The characteristics of the Sig you describe are what bother me somewhat about the conditioner. Do you own the 3.5 Sig PLUS?
Yes, and I'd highly recommend if you have the non plus to do the upgrade. It brings in all the good of the BPT Sig and none of the aformentioned characteristics that in some systems may not strike the best balance. To me it sounds like a completely different unit, not just an "upgrade". In my opinion it's a no brainer. Truly one of the best values in audio I've EVER found and easily worth the money. FWIW, I don't run my amps through it, but everything else goes through it.
I have owned both units as well. My findings are similar to Owl's. The BPT 3.5 Signature was excellent, however a bit closed in on top, or perhaps a bit dark overall. The 3.5 Signature PLUS not only seems more neutral in overall character, there is more extension in both treble and bass, and the noise floor is even quieter - no joke. I have my amps plugged into the unit, and Chris Hoff at BPT gave me the tip to try the amps plugged into both the "amp" plugs as well as the duplex next to it, as one has different sonic characteristics than the other, and system matching will determine which works best...

I personally feel the upgrade between the 3.5 Sig to the 3.5 Sig Plus was well worth the cost difference.
Thanks, Kirk. My impressions of the BPT 3.5 Sig are that it is velvety smooth and produces music that floats in an inky black background. However, compared to the Shunyata Hydra, it robs the music of some life and sparkle. It's the life and sparkle that I miss with the 3.5 Sig. Does this return with the Plus upgrade?
Has anybody heard the Audio Power Adept System? I got that as a rec. from another member. Also,he says in the same league; Sound Applcations,but didn't mention which model.He didn't care for the BPT Sig. model, and now I kinda understand.
Anytime Grant. Yes, in my experience the Sig Plus seems to posess more natural treble extension (shimmer & decay on a cymbal hit, etc.) while overall being more neutral and not as "slightly dark" overall as the Signature model was in my experience. There is also improvements in lowered noise floor, extension in bass, dynamics, and to me the midrange seems to have more "purity" per se... perhaps the lack of "slightly darker" tonal balance that I thought the Sig. model had. As I mentioned above, Chris @ BPT will tell you if you call him, to try the amp plugged both into the amp duplex as well as the duplex next to it, as they both have different sonic characteristics.
Thanks for the tip about trying adjacent duplexes, Kirk. I'll give that a

Addendum: 3/24/05 - I unplugged my amp from the BPT 3.5 Sig GFCI
duplex and plugged it into one of the standard duplexes instead. It
made all the difference; opened up the soundstage and brought the life
back into the music. Thanks, Kirk.