Yeah, I never quite got the 15V thing (maybe why no power switch). Second piece of gear I have with those that I will never use.
 
Right now I am focused on the glorified DI/stompbox aspect since I have been on this "baking binge" to minimize post-production work and can pass both wet/dry signals in. The downsides thus far as physical cabling I need to make/break for setups, and that I am swapping driver modes in SONAR more readily (although I am finding that SONAR switches itself properly if it can only see one device at a time).

Great that this worked out.  I'll keep my eye out for one in the used market.  One can never have too many Noyz Toyz

Quick update to this one just to better close out where I went with this (GNX3000 unit).
 
Drivers - The "ASIO" drivers that came with this appear to be similar to ASIO4ALL. WDM is actually faster, and programs came up with "GNX3000 not connected" when starting them. Latency is a "no go" in 95% of the cases, and since this "ASIO" driver is intrusive I uninstalled the driver set. As an "audio interface" this is not a recommended option.
 
X-Edit 2 - The GUI to "program the guts" works without the drivers (thank God), and is pretty indispensable for initial setup. As I intend to use this as DI/Solid State stomp box, I focused on setting up the first 5 user presets to be "normalized" on all amp channels (the channel switch has options for up to 1, 2, warped (mixed) and for all 5 presets I chose all to have 15 variations available). Setup for this takes a while, but when completed, the USB umbilical can be unplugged. Additionally, within X-Edit 2 there are options to simulate Humbucker->Single Coil and vice versa, as well as "simulating an amp performance through regular speakers." Nice features, but a huge con to these is that I have yet to find how to program into the stomp box potion (along with reverb which also seems "baked"). Another con is that the FX are set by preset, not channel, so all 3 channels of the same preset have the same FX in them - more of a nuisance as HB->SC is a nicety that would be better with a quick on/off. 
 
Connections - As my main use for this ATM is straight into my Saffire, I choose a headphone->L/R TS connection (Y-split) cable. As many patches internally generate stereo, this seemed the easiest way to capture both (and the volume knob on the unit is handy). For amp use, can simply run the mono amp output to a clean amp channel.
 
Thus far, the expression Pedal has yet to be (custom) programmed for anything, but will take up to 3 FX so want to think about how I would employ this going forward. Wah-Wah (enabled/disabled by pressure on the toe switch) and/or volume are programmed into many presets by default.

You may want to have a look here concerning presets :

http://www2.digitech.com/...art2.asp?productid=215

I have an RP 500 xlr out into LS56 mono. There are sound communities for most digitech setups and you can download the presets and tweak them with X-Edit, then load them to your unit. I also have a Boss ME80 which is far more complicatd to set up (nice sounds) and i still use the digitech when playing live. Would love to get a "Heritage" model like yours ! LOL

Don't understand your comment re Asio4All ? My RP 500 Asio works ok in Sonar, but my preference is to use via the LS 56.

Cheers,
Jerry

Yeah, I was going to mention the online presets as I downloaded the zip file a while ago (like 638 total). There are some useful ones in there, but the issue I had was the "normalizing." What I mean by this is many of them are way hot, and I spent a lot of time getting the channels to have consistent levels with the distortion on/off. I didn't want to have to adjust any gains while playing.
 
The drivers can be used for audio interface functions, with just a bit more latency than I would use (and do not need). The ASIO4ALL comment came from me shifting driver mode between WDM and ASIO (which I do often, and I only know of going through WDM to shift between two ASIO devices). That pop-up of the "GNX3000 not being connected" came up in multiple programs (not just SONAR) even with my Saffire as the only online device. The point where I removed those drivers was during a driver shift and clicking on Preferences->Audio->Driver Settings (just on the left tab) in SONAR would cause SONAR to crash. Thankfully, both the "Playback and Recording" and "Devices" were both accessible so I could get out of using it, but after I triggered that driver conflict twice I simply decided to remove it. I think most users would not see this, however, since it required a shift from WDM->ASIO mode in SONAR to trigger it.