I have the BLI PA's with their Paragon2.
Sound is really great.
Unfortunately, in my opinion, DC operation of sound is, well, a bit touchy. My experience is there are
various kinds of DC powerpacks, some work better than others with my Paragon2 PAs. The speed
control is sometimes touchy, takes a little bit of trial and error to understand how to 'feather the voltage' to
get your sound to match the speed and movement of the loco. Once you've done that, you have an OK
experience. I say "OK", not "great", because you really have to learn to "feather the voltage" to get any
sort of realistic correlation of sound and movement. It takes a fair amount of attention to do that. Also,
all the special effects (bell, horn, dynamic brakes, etc) are not intuitive to use on DC, if they are available at all.
That having been said, sound quality itself of both the BLI PA's and the BLI E8's that I have are superb
on DC as well as DCC. I would guess the E6's are going to be the same way.
Bu I would clearly say, that if you have any thoughts about going to DCC, do it if you are going to have sound
locos. It's said that sound sells DCC and DCC sells sound. It's true, it's like night and day.
There's nothing wrong with 'trying a sound loco on DC', I did that myself. But after trying it, I ended up
buying the NCE PowerCab for DCC, because I wasn't satisfied with DC operation of the Precision Craft Models E7s
(which are from same manufacturer as BLI). I found that was a good move to get the PowerCab,
it wasn't any more expensive than a couple of locos, and I then had the full
experience of sound. After you run your sound loco on DCC on a test loop,
you'll see what I mean.
You can read a little more about that on my layout at:
http://home.comcast.net/~j.sing/Peavine_Layout_Overview.html#DCCBy the way, my layout, I can switch it from all-DC to all-DCC (and swap locos on the track accordingly, of course).
That prevents me from having to decoderize everything. When I run sound locos, I just switch the layout
to DCC. And although I love DCC, the majority of my locos are still DC and run on the layout when it's in DC mode, as
there's too many to decoderize. So I have the best of both.
Hope that helps
Just my 2 cents worth.