1.) EXACTLY. When using a DT amp L6 Linked to the POD HD500, the proper protocol is to use the PRE models of the amps on the HD500 and let the DT handle the power amp modeling using it's tube resources. The HD500 via L6 link will configure the DT's amp class and topology accordingly. The DT tubes are at the power amp section "only" so you will be getting the full benefits of the DT and what it brings to the table. YOU WILL BE PLEASED!
2.) When you switch amp models in the DT you can physically hear the amps hardware adjust it's tube configuration to acheive the results of the amp you are wanting to emulate. What is unique about this is that modeling prior was done using software. The DT uses software/firmware and physically manipulates its tubes to achieve this. Does it sound exact? Some people will say over 90% exact. I will say that whatever sound I want to achieve, I can fully get there and sound pretty damn good to an audience doing it. That is the beauty in my mind. From clean, metal, to blues, to U2. You are getting multiple amps in one.
If you like the HD500, you are about to take it to a new level. The DT series amps are great standalone amps. On the flip side, The HD500 must have the DT amp to be fully realized IMO.
FYI: I use a DT50 with an HD500.
Thank you for your answer. What I am hearing is that I will notice a difference because the DT25 will manipulate the tube settings depending on the HD500 model picke, and that would be noticeably different from the HD500 model going into my Marshall tubes.
I would love to try out a DT25 with my POD, but I can't find a store with a DT25 in it. I am wondering if the difference described is worth the money, and only my ears can tell me that.
" What I am hearing is that I will notice a difference because the DT25 will manipulate the tube settings depending on the HD500 model picke, and that would be noticeably different from the HD500 model going into my Marshall tubes."
It's pretty amazing going from a VOX tone to a Soldano high gain tone in one amp. I wish you could try it to.
Funny story: I went to buy my amp and tried a line6 older model. It had all the effects built in. I played through it. It was completely uninspiring. I was going to buy it (I like convenience and flexibility) and I said to the clerk: " Before we wrap this up plug me into that line6 tube." The difference was night and day. The clerk told me before I plugged into the solid state that most people don't know the difference between a tube and solid state. Afterward I told him he was nuts and to wrap up the DT50.
One main complaint is that in the emulation many find issue getting a sustained volume level between amp models. It takes some work but the end result is worth it. If you had this variety of actual amps (with their hardware/tube variables) you would see the same behavior. The different sweet spots often rely at least partly on volume levels and how the tubes are used by the amp. There are excellent resources (users) on these forums.
I am getting a DR. Z. Airbrake today to help deal with that - especially for low volume practicing.
Good luck to you!