I think a lower low power would be more useful on an 8" scope. The 26mm Type 5 Nagler would be a great choice as a low-power eyepiece. Alternatively, the 22mm Type 4 Nagler.
If you didn't mind less eye relief, even the 24mm Panoptic would be a great choice.
I think a 17mm is a little high for a lowest-power.
The 12mm would be an excellent middle, and the 8mm Delos an excellent higher power. You could save a bit and get a 12 Delos as the middle power. That would hardly be a sacrifice. If you did that, I'd tend to go for the 22mm T4 Nagler as a low power, since its eye relief is closer to the Delos series and it has a wonderful immersive character to its field.
You'll want a good 2X 1.25" barlow to yield the higher powers. There are many good choices in the market. One of the best inexpensive ones is the 4-element Explore Scientific 2X Focal Extender, which works well with those eyepieces. The TeleVue 2X barlow is also good, but retails for more.
At one point, I owned the 12mm T4 Nagler and the 13mm T6 Nagler. I kept the 13 because it was better in my f/5 scopes in the outer 50% of the field and because it was superbly sharp. In my dob, I balanced its light weight with the 12 ounce brass "Equalizer" adapter from TeleVue. The eyepiece that replaced it, the 13 Ethos, didn't need the extra weight in the adapter.
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